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How to check an old-money account

A calculator can verify a total. To interpret an old account, you also need to preserve its units, headings and date. This constructed example takes you from a transcription to a result you can check and cite.

Start with the source, before converting anything

Photograph or transcribe the column headings as well as the figures. Three adjacent columns headed £, s and d are one amount in three units. A dot between the figures need not be a decimal point. Note whether the page records receipts, expenses, debts, quantities or unit prices.

The account below is an invented teaching example dated 1950. Its labels and amounts are chosen to demonstrate the arithmetic; they are not evidence of actual prices or spending patterns.

1. Add the three payments

Begin with the pence: 9 + 6 + 8 = 23d. Since 12d = 1s, write 11d and carry 1s. Then add the shillings: 15 + 7 + 6 + 1 carried = 29s. Since 20s = £1, write 9s and carry £1. Finally add the pounds: 2 + 1 + 0 + 1 carried = £4. The three payments total £4 9s 11d.

In the £sd calculator, put each payment on a plus line. The normalised total should agree. You can also convert each amount into old pence as an independent arithmetic check: 669d + 330d + 80d = 1,079d.

2. Subtract the money received back

Only subtract the fourth line if the account identifies it as money returned against these payments. Its position on the page alone is not enough. £4 9s 11d minus 4s 9d leaves £4 5s 2d. In old pence that is 1,079 − 57 = 1,022d.

Use a minus line for 4s 9d. A negative total would mean your subtraction exceeded the additions in this calculation; it would not by itself prove that the historical account holder was in debt.

3. Express the face value in decimal money

Divide 1,022 old pence by 240 old pence per pound: the result is £4.258333…, displayed as £4.26 to the nearest new penny. Keep £4 5s 2d as the exact original total. If every line were rounded to modern pennies before addition, small differences could accumulate.

Check £4 5s 2d in the converter. Decimal face value describes the same nominal pound in another notation. It is not the amount a present-day household would need to make equivalent purchases.

4. Add a dated price comparison, if useful

Using 1950 as the source year and 2025 as the comparison year, multiply the unrounded pounds by 1588.6 ÷ 33.0. The result is approximately £204.99 in 2025 prices. Reproduce this price comparison.

That ratio comes from the ONS CDKO annual price series. It is a broad price-index comparison. It does not establish the exact modern cost of the account's items, the earner's relative income or the value of a surviving object.

5. Leave a research note another person can follow

Illustrative 1950 account: three payments total £4 9s 11d; less 4s 9d returned gives £4 5s 2d (1,022 old pence). Decimal face value £4.258333…; approximately £204.99 in 2025 consumer prices using ONS CDKO annual indices 33.0 and 1588.6.

For a real account, add the archive or collection name, document reference, page or image number, and your transcription date. Preserve uncertain figures using a note rather than silently correcting the source to fit your expected total. A mismatch can come from carrying, a missing line, a misread fraction, a quantity column mistaken for money, or a mistake in the original.

Sources and next steps

The denomination relationships are described by the Royal Mint Museum. The arithmetic above is worked specifically for this guide. For the software's precision and data scope, read methods and sources; for a date in a heading, use the historical-date guide.