legal.retainer-drawdown Unreviewed

export function retainerDrawdown(onAccount: Money, bills: readonly RetainerBill[]): RetainerDrawdown

/** A bill the money on account may pay. */
export interface RetainerBill {
  readonly reference: string;
  /** the bill total, VAT and disbursements included; 0 or more */
  readonly amount: Money;
}

/** What happened to one bill. */
export interface RetainerApplication {
  readonly reference: string;
  readonly billed: Money;
  /** taken from the money on account */
  readonly applied: Money;
  /** still due from the client */
  readonly outstanding: Money;
}

/** The money on account after paying the bills. */
export interface RetainerDrawdown {
  /** in the order given */
  readonly bills: readonly RetainerApplication[];
  /** the total transferred from client account */
  readonly applied: Money;
  /** the total still due on the bills */
  readonly outstanding: Money;
  /** money left on account */
  readonly balance: Money;
}

import { retainerDrawdown } from "#fune/legal.retainer-drawdown@^1";

import { type Money, money } from "./money_amount.ts";  ← from money.amount ^1.0.0 · built alongside by fune
import { type RetainerApplication, type RetainerBill, type RetainerDrawdown } from "./legal_retainer_drawdown_types.ts";

/** Apply money on account to bills in the order given. */
export function retainerDrawdown(onAccount: Money, bills: readonly RetainerBill[]): RetainerDrawdown {
  const currency = onAccount.currency;
  if (onAccount.minor < 0) {
    throw new RangeError(`onAccount must not be negative, received ${onAccount.minor}`);
  }
  let left = onAccount.minor;
  let applied = 0;
  let outstanding = 0;
  const lines: RetainerApplication[] = [];
  for (const bill of bills) {
    if (bill.amount.currency !== currency) {
      throw new RangeError(`currency mismatch: ${currency} and ${bill.amount.currency}`);
    }
    if (bill.amount.minor < 0) {
      throw new RangeError(`bill "${bill.reference}" must not be negative, received ${bill.amount.minor}`);
    }
    const take = Math.min(left, bill.amount.minor);
    left -= take;
    applied += take;
    outstanding += bill.amount.minor - take;
    lines.push({ reference: bill.reference, billed: bill.amount, applied: money(take, currency), outstanding: money(bill.amount.minor - take, currency) });
  }
  return { bills: lines, applied: money(applied, currency), outstanding: money(outstanding, currency), balance: money(left, currency) };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 1 dependency, 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.retainer-drawdown

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

The whole function, every language, is one file too: legal.retainer-drawdown-1.0.1.fune, 21,835 bytes, sha256 ade1e11d776564d1508d4c2cc41781ad189fcdb156899d63768b15215bb91b9b. It installs into a project of any language.

// fune: before legal.retainer-drawdown

// fune: after legal.retainer-drawdown

// fune: replace money.amount in legal.retainer-drawdown

// fune: step legal.retainer-drawdown after <n|label>

More from the author

This is arithmetic only. Whether money may be taken at all is a regulatory question. Rule 4.3 of the SRA Accounts Rules (https://www.sra.org.uk/solicitors/standards-regulations/accounts-rules/) requires a bill of costs or other written notification of the costs to be given before client money is transferred to pay them, and the payment to be for the specific sum identified and covered by the money held for that client. Pass only bills that have been delivered, for one client and matter. Whether the last bill may be part-paid from what is left, as this does, or must wait until the whole sum is held, is a question for the firm's compliance officer (COFA); check `outstanding` on each bill and transfer nothing for a part-paid one if your firm reads the rule strictly. All amounts must be in one currency.

## 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 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 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.

1.0.1 marks it unreviewed. The code and the tests are unchanged.

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