legal.limitation-date Unreviewed

export function limitationDate(claimType: string, accrualDate: string, knowledgeDate: string | null): LimitationPeriod

/** The period that applies and the last day it allows. */
export interface LimitationPeriod {
  readonly claimType: string;
  readonly years: number;
  /** the section of the Limitation Act 1980 that sets it */
  readonly section: string;
  /** the accrual date, or the later date of knowledge where the section allows it */
  readonly runsFrom: string;
  /** the last day on which the claim may be brought */
  readonly expiry: string;
}

import { limitationDate } from "#fune/legal.limitation-date@^1";

import { parseIsoDate } from "./dates_add_days.ts";  ← from dates.add-days ^1.0.0 · built alongside by fune
import { addMonths } from "./dates_add_months.ts";  ← from dates.add-months ^1.0.0 · built alongside by fune
import { LIMITATION_PERIODS, LIMITATION_PERIODS_HISTORY } from "./legal_limitation_date_data.ts";  ← this capability’s own data, compiled from data/limitation-periods.json into the same file by fune build
import { type LimitationPeriod } from "./legal_limitation_date_types.ts";

/**
 * The last day to bring a claim: the anniversary of the accrual date (or the
 * later date of knowledge) the period's number of years on, the accrual day
 * itself excluded, and the month's last day where no anniversary exists.
 */
export function limitationDate(claimType: string, accrualDate: string, knowledgeDate: string | null): LimitationPeriod {
  parseIsoDate(accrualDate);
  const rows = LIMITATION_PERIODS.filter((r) => r.claimType === claimType);
  if (rows.length === 0) {
    const known = Array.from(new Set(LIMITATION_PERIODS.map((r) => r.claimType))).join(", ");
    throw new RangeError(`unknown claim type "${claimType}": expected one of ${known}`);
  }
  const rule = rows.find((r) => accrualDate >= r.validFrom && (r.validTo === null || accrualDate <= r.validTo));
  if (rule === undefined) {
    const earliest = rows.map((r) => r.validFrom).reduce((a, b) => (b < a ? b : a));
    if (LIMITATION_PERIODS_HISTORY !== "full" && accrualDate < earliest) {
      throw new RangeError(
        `no limitation rule for ${claimType} accruing on ${accrualDate}: this build was installed with history=${LIMITATION_PERIODS_HISTORY}, so it only carries rules from ${earliest}. Reinstall with history=full for older claims.`,
      );
    }
    throw new RangeError(`no limitation rule for ${claimType} accruing on ${accrualDate}`);
  }
  let runsFrom = accrualDate;
  if (knowledgeDate !== null) {
    if (!rule.fromKnowledge) {
      throw new RangeError(`a ${claimType} claim runs from accrual under ${rule.section}; knowledgeDate must be null`);
    }
    parseIsoDate(knowledgeDate);
    if (knowledgeDate > accrualDate) runsFrom = knowledgeDate;
  }
  // The corresponding date rule: the anniversary, clamped to the month end.
  const expiry = addMonths(runsFrom, rule.years * 12);
  return { claimType, years: rule.years, section: rule.section, runsFrom, expiry };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add legal.limitation-date

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./legal.limitation-date-1.0.1-typescript.fune, or fetch it from a terminal with fune pull legal.limitation-date@1.0.1:typescript.

The whole function, every language, is one file too: legal.limitation-date-1.0.1.fune, 29,851 bytes, sha256 e158c7c9b69f962c622dbfc6b5caa8b6ab3589271299976d4c6e4fe6c9c8f195. It installs into a project of any language.

// fune: before legal.limitation-date

// fune: after legal.limitation-date

// fune: replace dates.add-days in legal.limitation-date
// fune: replace dates.add-months in legal.limitation-date

// fune: step legal.limitation-date after <n|label>

More from the author

| claimType | years | from | section | |---|---|---|---| | contract | 6 | accrual | s.5 | | tort | 6 | accrual | s.2 | | personal-injury | 3 | accrual or date of knowledge, if later | s.11(4) | | fatal-accident | 3 | death or dependant's date of knowledge, if later | s.12(2) | | defamation | 1 | accrual (publication) | s.4A | | malicious-falsehood | 1 | accrual | s.4A | | deed | 12 | accrual | s.8(1) | | statute-sum | 6 | accrual | s.9(1) | | contribution | 2 | the judgment, award or agreement | s.10 | | recovery-of-land | 12 | accrual | s.15(1) | | rent-arrears | 6 | the date the arrears fell due | s.19 | | mortgage-principal | 12 | the date the right to the money accrued | s.20(1) | | mortgage-interest | 6 | the date the interest fell due | s.20(5) | | judgment | 6 | the date the judgment became enforceable | s.24(1) | | judgment-interest | 6 | the date the interest fell due | s.24(2) |

**Counting.** The day the cause of action accrues is excluded (Marren v Dawson Bentley & Co Ltd [1961] 2 QB 135), and a period of years ends on the corresponding date, the anniversary (the corresponding date rule, Dodds v Walker [1981] 1 WLR 1027, HL). So a contract breached on 15 March 2020 may be sued on until the end of 15 March 2026, and that date is `expiry`: the last day the claim may be brought. Where there is no corresponding date, the period ends on the last day of that month: a cause of action accruing on 29 February 2020 expires on 28 February 2026 (and on 29 February 2024 for a 4-year period, if there were one). Adding 365 days a year, or subtracting a day from the anniversary, gives the wrong answer; the vectors show both.

**Date of knowledge.** For personal injury and fatal accident claims the period runs from the later of accrual (or death) and the date of knowledge defined in s.14. Pass that date if one is asserted; the answer is only as good as it is, and whether a claimant had knowledge on a given date is exactly the kind of question this does not decide. Other claim types do not run from knowledge under these sections, so a knowledge date for them is an error rather than being silently ignored (latent damage in negligence under s.14A, which does, is not covered).

**Dates in force.** Every row applies to causes of action accruing on or after 1 May 1981, when the Act came into force (s.41(2)); defamation and malicious falsehood use the one-year period for causes of action accruing on or after 4 September 1996 (Defamation Act 1996 s.5, which by s.20(2) does not affect causes of action arising before). An earlier accrual date is an error, not an answer: the old periods are not carried.

## What this deliberately does not do

- Extensions and postponements: disability (s.28), fraud, concealment or mistake (s.32), acknowledgement or part payment (ss.29-31), the court's discretion to disapply the personal-injury periods (s.33), and the defamation discretion (s.32A). - Latent damage (ss.14A, 14B, including the 15-year longstop), product liability (s.11A, 10-year longstop), theft (s.4), loans without a date for repayment (s.6), buildings (s.4B), and every limit outside this Act (employment tribunals, judicial review, the Equality Act, contractual time bars, other jurisdictions). - When the last day falls on a day the court office is closed: the claim may generally be issued on the next day it is open (Pritam Kaur v S Russell & Sons Ltd [1973] QB 336), but whether that applies to a given claim and filing route is a question for the solicitor; `expiry` is the unextended date. - Which date the cause of action accrued on. That is the legal question, and it is the caller's input.

## Sources

Limitation Act 1980 (c. 58), latest version on legislation.gov.uk, read on 23 September 2026: sections 2, 4A, 5, 8, 9, 10, 11, 12, 15, 19, 20, 24 and 41, https://www.legislation.gov.uk/ukpga/1980/58/contents; section 4A amendment note (Defamation Act 1996 ss.5, 20(2), from 4 September 1996), https://www.legislation.gov.uk/ukpga/1980/58/section/4A.

A change to a period is a new version of this capability with a new row; the rows declare effective dates, so a `history=current` build refuses a date before its horizon rather than answering it with today's rule.

## Before you rely on this

**Not professional advice.** This capability calculates legal figures from published rules. It is a software component for developers, not legal advice. Rules change and every rate here has an effective date. Check that the dates cover your case. Verify results against the official sources listed above, and have a litigation solicitor review how you use it, before anyone relies on the output. Provided "as is" under its licence, without warranty.

**Unreviewed.** This capability's implementations agree in every language and pass its published test vectors, which were worked out from the official sources cited. But no qualified litigation solicitor has yet checked those vectors, or confirmed that the capability covers the cases it claims. Treat it as a draft. Do not use it for real people, money or decisions without your own expert review. Once a qualified reviewer signs off, this notice is replaced with their name, qualification and the date. Each new version needs fresh sign-off.

## Notices

Contains public sector information licensed under the Open Government Licence v3.0 (https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/).

Legislation: Crown copyright and database right.

1.0.1 marks it unreviewed and adds its attribution notices (NOTICE). The code and the tests are unchanged.

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