Glossary

Plain-English definitions. Use the filter to find a term.

Address poisoning

Scam that plants a look-alike address in your transaction history hoping you copy it.

Administration period

The time from death until everything in the estate has been passed on, during which the personal representative is responsible for the assets (GOV.UK). See UK guide.

aezeed

LND's 24-word Lightning wallet seed format; uses the BIP39 wordlist but is not BIP39-compatible.

Air-gapped

A device that never connects to a network or computer by cable/wireless; data passes by QR code or memory card.

Anti-exfil signing

A signing protocol in which the computer contributes randomness to each signature, so a malicious device cannot hide your seed in signatures. Called anti-klepto by BitBox. See verifying firmware.

Attach to PIN (Ledger)

A Ledger option that links a BIP39 passphrase to a second PIN, so entering that PIN opens the passphrase accounts. The passphrase itself is not kept, but the derived keys stay on the device until it is reset; the written passphrase is still the only backup. See how wallets differ.

Authenticity check

A maker's test, usually run in its official app, that the device is genuine and running signed firmware. See setup checklist.

Backup inventory

A written list of every backup item and device, where each is kept and when it was last checked, without any of their contents. See the inventory template.

Basic exclusion amount

The amount a US estate (together with lifetime taxable gifts) can pass free of federal estate and gift tax: $15,000,000 for 2026 deaths under P.L. 119-21. See US guide.

BIP

Bitcoin Improvement Proposal — a published design document (e.g. BIP39).

BIP32

Standard for hierarchical deterministic (HD) wallets: many keys from one master seed.

BIP38

Standard for encrypting a single private key with a password, common on older paper wallets.

BIP39

Standard for encoding a seed as 12–24 words from a 2,048-word list with a checksum.

BIP39 passphrase

Optional extra secret ("25th word") that creates a different wallet from the same words.

BIP39 wordlist

The list of 2,048 words a BIP39 phrase is drawn from. The English list is designed so the first four letters identify each word; ten languages exist, but BIP39 strongly discourages non-English lists. See fundamentals.

BIP44 / 49 / 84 / 86

Standard derivation paths for legacy, nested SegWit, native SegWit and Taproot addresses.

BIP85

Standard for deriving independent child seeds, passwords or keys from one master seed.

Blind signing

Approving a transaction without being able to read what it does on your device's screen.

Brain wallet

Wallet derived from a memorised phrase — insecure; routinely cracked.

BSMS (BIP-129)

Bitcoin Secure Multisig Setup: a procedure for safely exchanging xpubs and verifying a multisig descriptor.

CARF (Crypto-Asset Reporting Framework)

An OECD standard under which crypto-asset service providers report users' transactions to tax authorities, which then exchange the data internationally. First exchanges start in 2027, 2028 or 2029 depending on the country. See cross-border notes.

Casino dice (precision dice)

Dice machined to tight tolerances with sharp edges and flush-filled pips, so each face is closer to equally likely than with rounded dice. See dice bias.

Casualty loss

In US tax, damage or loss from a sudden, unexpected or unusual event. Personal casualty and theft losses are deductible only for declared disasters (IRC §165(h)(5)), now permanently. See lost or stolen crypto.

Caveat (probate)

A notice entered before a grant of probate to stop it being issued while a dispute, for example over who should apply or whether the will is valid, is resolved. See UK guide.

Centre punch

A pointed steel tool struck (or spring-loaded) to make a dot. Used to mark letters on grid-style metal backup plates; a light strike can be repeated in the same spot. See device design.

Check backup (dry-run recovery)

A hardware wallet mode in which you enter your backup on the device and it confirms whether it matches the stored wallet, without replacing it. Trezor calls it "Check backup"; Ledger offers a Recovery Check app. See the drill log.

Checksum

Extra data that lets software detect typing errors. In BIP39 it is part of the last word; it adds no security (why).

Chi-squared test

A statistical test that compares observed counts (for example, how often each die face appears) with the counts expected if every outcome were equally likely. See the dice worksheet.

Chief Counsel Advice

Written advice from the IRS Office of Chief Counsel to IRS staff, published in redacted form. It cannot be cited as precedent but shows how the IRS reads the law. See lost or stolen crypto.

Clipper (clipboard malware)

Malware that replaces a copied crypto address with the attacker's. Defeated by checking the full address on the hardware wallet screen. See safety.

Codex32 (BIP-93)

Hand-computable encoding and secret-sharing scheme for BIP32 seeds.

Coin type (SLIP-44)

The number in a derivation path that identifies the blockchain, such as 0 for Bitcoin and 60 for Ether, registered in SLIP-44. See the BIP family.

Coinjoin coordinator

A server that organises coinjoin transactions, in which several users combine payments to improve privacy. It cannot take funds but can see some metadata. See the directory.

Cold storage / cold wallet

Keys kept on a device that is not connected to the internet.

Collaborative custody

Multisig where a service holds one key and you hold the rest.

Commingling

When a custodian holds different customers' assets together instead of separately for each customer. The SEC suggests asking whether a custodian does it. See custody questions.

Commit-and-reveal

A protocol in which one party fixes (commits to) a secret value before seeing the other party's input, and later reveals it so the result can be checked. Trezor's entropy check uses it. See verifying a device.

Community property

A US marital property system (nine states, plus optional systems in three more) in which most property acquired during marriage belongs to both spouses equally; it can give both halves a stepped-up basis at the first death. See US guide.

Community property survivorship agreement (Texas)

A written agreement signed by both spouses that community property passes to the survivor on death, outside the will. It cannot be inferred from a joint or "JT TEN" account alone. See US guide.

Confirmation (Scotland)

Scottish equivalent of a grant of probate, issued by the sheriff court. See UK guide.

Controller (Northern Ireland)

A person appointed through the High Court's Office of Care and Protection to manage the property and affairs of someone who lacks capacity, the NI equivalent of a deputy. See UK guide.

Cost basis

What you paid for an asset, plus allowable costs, used to work out a gain or loss. The UK uses pooled costs; the US tracks basis by unit, wallet or account. See tax records.

Counterparty risk

The risk that the firm holding your assets fails, freezes withdrawals or is hacked. It applies to exchange balances, not to coins in self-custody. See custody.

Court of Protection deputy

In England and Wales, a person authorised by the Court of Protection to make decisions for someone who lacks mental capacity: property and financial affairs, personal welfare, or both. See UK guide.

CSPRNG

Cryptographically secure pseudo-random number generator: an algorithm that stretches a secret, truly random seed into unpredictable output. It cannot create entropy it was never given. See TRNG vs CSPRNG.

Custodian

A company that holds keys on your behalf.

DAC8

The EU directive that applies CARF-style crypto reporting inside the EU from 1 January 2026, with the first exchanges of 2026 data by 30 September 2027.

Death claim (executor services)

An exchange's process for releasing a deceased customer's account to the executor, usually needing a death certificate, probate documents, ID and a signed letter. See UK vs USA.

Decoy wallet

A wallet with a small balance to hand over under duress.

Deed of variation

A written document, made within 2 years of a death, by which UK beneficiaries redirect what they inherit; with the right statement it is treated for tax as if the deceased had made the change. See UK guide.

Deemed disposition

A tax rule (e.g. Canada, South Africa) treating assets as sold at market value at death, so the gain is taxed although nothing was sold. See the cross-country comparison.

Derivation path

The "route" from master key to a specific address, e.g. m/84'/0'/0'/0/0.

Descriptor (output descriptor)

Text describing exactly how a wallet derives its addresses; vital for multisig recovery.

Dice entropy

Using physical dice rolls as the random source for a seed.

Diceware

A way to make passphrases by rolling five dice per word and looking the number up in a 7,776-word list; each word adds about 12.9 bits. See passphrase entropy.

Drainer (wallet drainer)

Phishing software that asks you to approve transactions or permissions that send your assets to criminals. It does not need your seed. See Inferno Drainer.

Durable power of attorney

A US document appointing an agent to manage your financial affairs that stays in effect if you lose capacity. See the US guide.

Duress PIN

A PIN that opens a decoy wallet or wipes the device.

ECDSA nonce

The one-time secret random number used in each ECDSA signature. If it is repeated or even partly predictable, the private key can be computed. See biased nonces.

Electrum seed

The recovery phrase format created by Electrum 2.0 and later. It uses the same English words as BIP39 but encodes a version number in a hash of the words, so it is not a BIP39 phrase. See which standard?

Emergency access

A password-manager feature that lets a named person request access to your vault, granted automatically if you do not reject it within a wait period. Not a place for seed phrases. See digital copies of seeds.

Emergency Kit (Muun)

Muun's backup: a PDF with encrypted keys, descriptors and instructions, used together with a separately written Recovery Code instead of a seed phrase. See the directory.

Enduring power of attorney (EPA, Northern Ireland)

The NI power of attorney for property and money; it continues after loss of capacity once registered with the Office of Care and Protection. See UK guide.

Entropy

The amount of unpredictability, measured in bits; 128 bits is the modern minimum for seeds.

Entropy check

Trezor Suite feature (2025) in which the device commits to its own randomness before receiving the computer's, then proves on throwaway rounds that it combined both as documented. See verifying a device.

Escheat

In the US, the transfer of abandoned property, including the contents of an unpaid safe deposit box, to a state's unclaimed-property office. See safe deposit boxes.

European Certificate of Succession

A document issued under the EU Succession Regulation that proves an heir's, executor's or administrator's status in participating EU states (not Denmark or Ireland). See EU rules.

Excepted estate

A UK estate that does not need a full IHT400 account; the executor gives three values on the probate or confirmation application instead. See UK guide.

Executor / personal representative

The person legally responsible for administering an estate.

Extendable backup (SLIP-39)

A flag in SLIP-39 shares that lets more shares or groups be added later for the same wallet. Trezor uses it for upgrading single-share backups; older importers may not read such shares.

Extended private key (xprv)

The private counterpart of an xpub. Anyone holding it can spend from every key below it. Never store it in a "non-secret" descriptor or share it with a service.

Fault injection (glitching)

A physical attack that disturbs a chip's power, clock or (with a laser) its silicon at a precise moment to skip security checks. Used to extract seeds from chips without a secure element. See advisories.

FBAR

The US Report of Foreign Bank and Financial Accounts (FinCEN Form 114). FinCEN Notice 2020-2 said accounts holding only virtual currency are not currently reportable, but that it intends to change this. See moving abroad.

FDIC

Federal Deposit Insurance Corporation, which insures deposits at US banks. It lists crypto assets among the products it does not insure. See custody.

Financial Ombudsman Service

The free UK service for complaints against financial firms. Report Fraud says most crypto activity is unregulated, so complaints about it are usually outside its reach. See custody.

Fingerprint (master fingerprint)

8-character identifier of a seed that reveals nothing secret.

Fire rating (UL 72, EN 15659, EN 1047-1)

Test standards for how long a safe keeps its contents below a temperature limit (for paper, 177 °C under UL Class 350 and 170 °C under EN 15659). They do not cover burglary or floodwater. See safe ratings.

Flashover

The stage of a room fire when everything in the room ignites almost at once. NIST gives about 1,000 °C inside a room undergoing flashover. See house fire temperatures.

Forced heirship

Rules that reserve part of an estate for close family, such as the French réserve héréditaire, the Spanish legítima, the German Pflichtteil and the Japanese iryūbun. See things that differ by country.

Form 1041

The US income tax return filed by the fiduciary of an estate or trust to report its income, gains, losses and distributions. See US guide.

Form 1099-DA

A US form on which brokers report digital asset sale proceeds, for transactions from 1 January 2025, and basis for certain transactions from 2026. See tax records.

Form 706

The US federal estate (and generation-skipping transfer) tax return, due nine months after death where required, or filed to elect portability. See US guide.

Form 8949

The US form for reporting sales and other disposals of capital assets; digital asset sales use boxes G to L. See tax records.

Form E

The financial statement used in divorce and dissolution financial cases in England and Wales. It requires full, frank and clear disclosure, including crypto under "other assets". See divorce.

FSCS

Financial Services Compensation Scheme, the UK scheme that can compensate customers of failed authorised firms. The FCA says crypto losses are highly unlikely to be covered. See UK vs USA.

Galvanic corrosion

Corrosion that happens when two different metals touch in the presence of moisture, for example steel fasteners on a titanium plate. Avoid mixing metals in a backup. See materials.

Gap limit

How many unused addresses in a row a wallet checks before it stops looking for funds. BIP44 sets 20. Funds beyond the gap can look "missing" after a restore. See restore checks.

Guardianship order (Scotland)

A sheriff court order appointing a guardian to manage an adult's welfare, property and finances, or both, over the long term. See UK guide.

Habitual residence

The usual test under the EU Succession Regulation for which country's law governs an estate, unless the will chooses the law of the person's nationality.

Hardened derivation

A way of deriving child keys in BIP32 that needs the parent private key, shown with an apostrophe (for example 84'). It stops a leaked child key, combined with an xpub, from exposing the parent. See xpub risks.

Hardware wallet

Dedicated device that stores keys and signs transactions offline.

Health tests

Continuous checks on a hardware random source (e.g. NIST SP 800-90B's Repetition Count and Adaptive Proportion tests) that stop it if it fails. They catch broken hardware, not a well-behaved but predictable generator.

Hot wallet

Wallet on an internet-connected device.

IHT

UK Inheritance Tax: 40% on the estate above the available nil-rate bands, generally payable by the end of the sixth month after death. See UK guide.

Impersonation token

A token made to look like a well-known one, such as a stablecoin, often used in address poisoning (FBI Denver). See address poisoning.

Inactive Account Manager

Google's setting that shares chosen data with trusted contacts (or deletes the account) after 3–18 months of inactivity. See the directory.

Information-theoretic security

Security that does not depend on an attacker's computing power. Fewer than the threshold of Shamir shares reveal nothing about the secret, however much computing is thrown at them. See the numbers.

Intervention order (Scotland)

A sheriff court order authorising a specific one-off action for an adult with incapacity, such as signing a document or selling property. See UK guide.

Intestacy

Dying without a valid will. The state's (or, in the UK, the nation's) intestacy rules then decide who inherits, and a court appoints an administrator. See US guide.

Lasting Power of Attorney (LPA)

England & Wales legal document appointing someone to act for you; it must be registered with the Office of the Public Guardian before use. Scotland uses continuing powers of attorney and Northern Ireland enduring powers of attorney. See UK guide.

Lattice attack

A mathematical technique that recovers a private key from many signatures whose nonces are slightly biased or share bits. See biased nonces.

Legacy Contact

Apple's name for a person who can request your iCloud data after your death, using an access key and a death certificate. Keychain passwords are excluded. See the directory.

Legal rights (Scotland)

The right of a surviving spouse, civil partner and children to claim a share of the moveable estate whatever the will says.

Letter of instruction

Non-binding document telling executors what exists and how to access it — without secrets.

Letter of wishes

A UK term for an informal, signed note that guides executors or trustees. It is not legally binding, need not be witnessed and stays private when a will becomes public. See the UK supplement.

Letters testamentary

A US court document confirming an executor's authority to act for an estate (letters of administration if there is no will). See the US timeline.

Malvertising

Malicious adverts, including search adverts for look-alike sites. The FBI warned about them in December 2022. See safety.

Mersenne Twister

A fast, widely used statistical pseudo-random generator (mt19937). Its output can be predicted from its seed or from enough output, so it must never generate keys; it was at the heart of Milk Sad and the Trust Wallet extension flaw. See Milk Sad.

MiCA

EU Markets in Crypto-Assets Regulation.

Min-entropy

The worst-case unpredictability of a source, −log₂ of the most likely outcome's probability; the conservative measure used for keys. See estimation.

Miniscript

A structured language for Bitcoin spending policies, used for timelocked recovery.

Miscellaneous itemised deduction

A US category of deductions (spelt "itemized" in US law) suspended by §67(g) from 2018 and, after Public Law 119-21, permanently. See lost or stolen crypto.

MPC

Multi-party computation — key shares that sign jointly without ever forming one key.

multi() and sortedmulti()

The two multisig forms in output descriptors (BIP383). multi() keeps keys in the order listed; sortedmulti() sorts them. The same keys give different addresses under each, so the descriptor must record which. See multisig recovery.

Multipath descriptor (BIP-389)

A draft extension to output descriptors that lets one descriptor describe several paths, such as <0;1> for receive and change.

Multisig

Wallet needing M of N independent keys to spend.

Naive seed splitting

Storing parts of a seed's words in different places (for example words 1–12 and 13–24). Each part leaks most of the secret; use SLIP-39 or multisig instead. See the anti-pattern.

Negligible value claim

A UK claim that an asset has become of negligible value, letting a loss be crystallised. HMRC says it may be possible when there is no prospect of recovering a lost private key (CRYPTO22400). See tax records.

NFC backup card

A smart card that stores a wallet's backup and is read by tapping it on a device or phone, such as DCENT's R3covery card. It usually has its own PIN. See the directory.

NFKD normalisation

A Unicode rule BIP39 applies to words and passphrases so that characters typed differently are treated the same. Accented or non-Latin passphrases can still behave differently across devices; plain ASCII is safest.

Nil-rate band

The part of a UK estate taxed at 0% for Inheritance Tax: £325,000, fixed until 5 April 2031.

Nominee

A person named to receive or deal with an asset on death. In India a nominee for securities does not become the owner (Supreme Court, 2023). See India.

Official Administrator

In Hong Kong, the Registrar of the High Court, who can administer small estates of cash, sole bank accounts and MPF up to HK$150,000 without a grant. See Hong Kong.

Passphrase wallet (hidden wallet)

The separate wallet opened by a seed plus a particular passphrase. Every passphrase, including a typo, opens a valid, usually empty one. See passphrase pitfalls.

PBKDF2

A key-stretching function. BIP39 runs it with HMAC-SHA512 and 2,048 iterations to turn words and passphrase into the 512-bit seed. See from words to addresses.

Permit signature (ERC-2612, Permit2)

An off-chain signed message that grants a token allowance. It can be used later by whoever holds it, which makes it a favourite of drainers. See safety.

Polyseed

A 16-word Monero seed format that embeds the wallet's restore height.

Port-out fraud

Moving a victim's phone number to a different provider without permission, similar to a SIM swap. US FCC rules adopted in November 2023 address both. See safety.

Portability (DSUE)

The US election, made on a timely Form 706, that lets a surviving spouse use the deceased spouse's unused exclusion amount. See US guide.

Potentially exempt transfer (PET)

A UK lifetime gift to an individual that is free of Inheritance Tax if the giver survives 7 years; taper relief reduces the tax if death occurs 3 to 7 years after the gift.

Pour-over will

A will that leaves anything not already in your revocable living trust to that trust, so stray assets end up under the trust's terms (usually after probate). See US guide.

Pre-seeded device

A hardware wallet that arrives with a recovery phrase already chosen by someone else, for example on a card in the box. Whoever chose it can take the funds. See the eBay case.

Private key

Secret number that authorises spending from an address.

PRNG (pseudo-random number generator)

An algorithm that produces random-looking numbers from a starting seed. Ordinary PRNGs are predictable; only cryptographically secure ones (CSPRNGs), properly seeded, are suitable for keys. See true randomness.

Probate

Court process confirming a will and authorising executors.

Proper advice (Scotland)

Under s.19 of the 2024 Act, once in force: advice from someone the trustees reasonably believe is qualified by ability and practical experience, which trustees must normally get before investing. See the 2024 Act.

Prospective (legislation)

legislation.gov.uk's label for a provision that has been passed but not yet brought into force. See an example.

PSBT

Partially Signed Bitcoin Transaction (BIP-174), used for air-gapped and multisig signing.

Qualified custodian

A US term for a regulated firm, such as a bank or trust company, that may hold assets for clients of investment advisers. Gemini and Kraken describe their custody services as qualified. It does not mean insured against every loss. See the custodians in the directory.

Quorum (threshold)

The number of shares, keys or signatures needed out of the total, written m-of-n (for example 2-of-3). See Shamir vs multisig vs MPC.

Recovery drill

A planned rehearsal of recovering a wallet from its backups, and of an executor finding the papers, recorded in a log. See the drill log.

Recovery room

The FCA's term for scammers who contact people who have already lost money and offer to recover it for an upfront fee. See recovery scams.

Rehypothecation

When a custodian lends out or reuses customer assets for its own purposes, such as lending. See custody questions.

Reproducible build

Firmware that anyone can rebuild from the published source and get a byte-for-byte match with what the maker ships (apart from signatures), proving the source is what runs. See verifying firmware.

Residence nil-rate band

An extra UK Inheritance Tax allowance of up to £175,000 when a home passes to direct descendants; tapered away for estates over £2 million.

Revocable living trust

A US trust you control during life; assets titled to it generally avoid probate, and a successor trustee can act on death or incapacity. See will or trust.

RUFADAA

US Revised Uniform Fiduciary Access to Digital Assets Act: 49 of 53 US jurisdictions had enacted it by October 2026. See which states.

Schedule 7 (Terrorism Act 2000)

A UK power that lets examining officers question and search people at ports and borders. People examined must give information requested, and wilful obstruction is an offence. See border checks.

Sealed access instructions

Instructions on how to restore wallets, kept sealed and opened only on death or incapacity. They should never put a whole seed and its passphrase in one place. See UK guide.

Section 104 pool

HMRC's pooling of each type of token into a single asset with an average cost, after same-day and 30-day matching (CRYPTO22200). See tax records.

Secure element

Tamper-resistant chip designed to protect secrets from physical extraction. Some devices run the whole wallet inside it (Ledger); others use it to guard the PIN and secrets while a general chip does the rest (Trezor Safe, BitBox02, COLDCARD). See security models.

Security bond

A type of insurance a property and affairs deputy may have to set up before appointment, protecting the finances of the person they act for. See UK guide.

Seed phrase / recovery phrase / mnemonic

Human-readable words encoding your wallet's master secret.

Seed XOR

Splitting a seed into N valid seeds that XOR together; all parts needed.

SeedQR

QR encoding of seed words for air-gapped signers.

Self-custody

Holding your own private keys, for example on a hardware wallet, so that no firm can freeze or lose your coins, and no firm can recover them for you either. See custody basics.

setApprovalForAll

An NFT approval that lets another address manage all of your NFTs from one collection. MetaMask notes you should not need one to receive a free NFT. See safety.

Shamir's Secret Sharing

Method to split a secret into shares, any M of which reconstruct it.

Share identifier (SLIP-39)

A random 15-bit number shared by every share in one SLIP-39 set. It makes shares of a set start with the same two words and stops shares from different sets being mixed. See telling sets apart.

SIM swap

When a criminal has your phone number moved to their own SIM card, so that they receive your calls and text-message login codes. See moving off an exchange.

Single point of failure

One item whose loss or exposure is enough to lose the funds, such as the only seed copy or a missing multisig descriptor. See single points of failure.

SIPC

Securities Investor Protection Corporation, which protects cash and securities at failed US brokerages. It does not protect crypto assets that are not registered securities. See UK vs USA.

Situs

The legal location of an asset for tax purposes. HMRC's view is that an exchange token with no underlying asset is located where its beneficial owner is resident (CRYPTO22600).

SLIP-10

A SatoshiLabs standard extending BIP32-style derivation to other curves such as ed25519, where only hardened derivation is supported. See fundamentals.

SLIP-132

A registry of extended-key prefixes such as ypub and zpub that signal the address type. It is a convention outside BIP32; descriptors are the more portable record.

SLIP-39

SatoshiLabs standard for Shamir shares as 20- or 33-word mnemonics.

Small estate affidavit

A sworn statement that lets a successor collect a small estate's property without full probate, within limits set by each US state (California: $208,850 for deaths from 1 April 2025; Illinois: $150,000 from 15 August 2025). See six-state table.

Source-available licence

Code you can read but whose licence restricts some uses (for example COLDCARD's MIT + Commons Clause), so it is not open source in the OSI sense.

Sovereign (external) recovery

Moving funds from a collaborative-custody wallet with your own keys and open-source software, without the provider. See collaborative custody.

SPDI (special purpose depository institution)

A Wyoming bank charter designed for digital asset businesses; Kraken Financial holds one.

Special destination (Scotland)

A clause in a title, such as "to A and B and the survivor", that passes property to the survivor outside the will. After divorce or dissolution the former spouse is treated as having died first, unless the title says otherwise. See the 2024 Act.

Stainless steel grades (304 / 316 / 316L)

Common corrosion-resistant (austenitic) steels used for metal backups. 316 resists salt better than 304; 316L has lower carbon for extra resistance where the surface has been punched. See materials.

Stateless signer

Device that stores nothing; you load the seed each time (e.g. SeedSigner).

Statutory legacy

The fixed sum a surviving spouse or civil partner takes first under the intestacy rules of England and Wales: £322,000 for deaths on or after 26 July 2023 (GOV.UK). See UK guide.

Step-up in basis

US rule resetting cost basis to market value at death.

Successor trustee

The person or firm named to take over a trust when the creator dies or becomes incapacitated; for a funded trust they can act without court letters. See US guide.

Summary administration (Florida)

A shortened Florida probate procedure, by court order, for estates subject to administration worth $75,000 or less (after exempt property) or where the person died more than two years ago. See small-estate limits.

Supply-chain attack

Tampering with a product or software component before it reaches you — for example a counterfeit device or a poisoned code library. See supply chain.

Tamper-evident bag

Serial-numbered bag that shows if opened. Record the serial number and inspect it on a schedule; see maintaining stored backups.

Taproot (P2TR)

A Bitcoin output type whose single-key wallet accounts use purpose 86' (BIP86) and addresses starting "bc1p". See the BIP family.

Tell Us Once

A free UK government service that reports a death to most government departments and councils at once. It does not notify private firms such as exchanges. See the directory.

Temporary non-residence (UK)

HMRC rules under which some gains made while abroad are taxed when you return to the UK if you were away for five years or less. See moving abroad.

Test transaction

A small transfer sent first to check that the address and network are right before sending the full amount. See first week.

Test vectors

Published example inputs and outputs used to check that software implements a standard correctly. Their phrases are public, so they must never hold funds.

Theft loss

In US tax, a loss from conduct that is theft under state law. IRS Chief Counsel memo 202511015 says some scam losses in profit-seeking transactions may be deductible. See lost or stolen crypto.

Third category of personal property

In England and Wales, things such as crypto-tokens that are neither physical things nor rights against a person, confirmed as capable of being property by the Property (Digital Assets etc) Act 2025. See the case file.

Timelock

Condition that prevents spending until a time or block height.

Token approval (allowance)

Permission for an app to move a type of token from your wallet, often for an effectively unlimited amount. Revoking it costs a fee and cannot recover tokens already taken. See safety.

Transfer-on-death (TOD) designation

A beneficiary registration that passes an account outside probate at death, where the provider offers one. The major exchanges checked by this site do not. See US guide.

Travel Rule

Rules that require crypto firms to collect and share information about the sender and recipient of transfers. In the UK they have applied since 1 September 2023. In the US, FinCEN's Funds Travel Rule (31 CFR 1010.410(f)) covers transmittals of $3,000 or more, including crypto. See custody.

TRNG

True random number generator based on physical noise; its raw output is usually health-tested and conditioned before use.

Trusts and Succession (Scotland) Act 2024

A Scottish Act modernising trust law (trustee powers, investment, delegation, duty of care) with small succession changes. Only parts were in force in October 2026. See commencement status.

Unclaimed property

In the US, assets such as dormant accounts that holders must report and hand to a state after a dormancy period; can include crypto on exchanges. See also Escheat and the directory.

Unhosted wallet

The regulators' term for a self-custody wallet that no crypto firm controls. Also called a self-hosted wallet. See moving off an exchange.

Uniform Law Commission (ULC)

The US body that drafts model "uniform acts", such as RUFADAA, for states to adopt; it tracks which states have enacted each one. See RUFADAA by state.

Unsecured creditor

Someone owed money by an insolvent firm without any claim on specific assets. Customers of a failed custodian can end up in this position. See custodian failure.

Valuation date (Irish CAT)

The date at which an inheritance is valued for Capital Acquisitions Tax — often when the executor can retain or hands over the asset, not the date of death. See Ireland.

Vanity address

An address deliberately "ground" to contain chosen characters. Tools that make them have used weak seeds, as in the Profanity case. See Profanity.

Voluntary administration (New York)

New York's procedure for small estates with $50,000 or less of personal property, handled by a voluntary administrator without full court administration (SCPA Article 13). See small-estate limits.

Von Neumann debiasing

Turning biased but independent coin flips into fair bits by flipping in pairs, keeping HT/TH and discarding HH/TT. See coin flips.

Wallet birthday

The date a wallet or descriptor was created, recorded so a restore can scan the blockchain from the right point. See descriptor records.

Wallet configuration file

A file (often JSON or a descriptor) that lists the public keys, derivation paths and script of a multisig wallet; needed with the keys to rebuild it. It cannot spend on its own but reveals balances. See single points of failure.

Wallet fingerprint

A short public code identifying a master key; useful for checking a restore without revealing anything secret.

Wallet policy (BIP-388)

A compact way to register a multisig or other script wallet on a hardware device so it can verify addresses and change. Used by Ledger's Bitcoin app. See multisig across vendors.

Wallet-by-wallet basis

The US rule, from 1 January 2025, that digital asset basis is tracked separately for each wallet or account (Rev. Proc. 2024-28). See housekeeping.

Watching-only wallet

A wallet that holds only public keys (an xpub or descriptor), so it can show balances and build unsigned transactions but cannot spend. Used with offline signing.

Wrench attack

Physical coercion to make someone hand over crypto.

xpub / zpub

Extended public key: reveals addresses and balances but cannot spend.