When a business has not kept full books, accounts are rebuilt from what does exist: bank statements, invoices, a list of assets and liabilities, and known relationships such as the usual mark up. The standard tools are an opening statement of affairs, reconstructed control accounts and cash accounts, gross profit percentages, and, where almost nothing exists, the net worth method, which finds profit from the change in net assets adjusted for drawings and capital introduced.

What counts as incomplete records?

ACCA’s technical article on the subject identifies two situations: there are no records at all, or some records exist and the missing figures can be calculated from them. The second is far more common. A typical client has bank statements and some sales invoices, but no sales ledger, no record of cash takings banked or spent, no stock count and no note of what was taken for personal use.

The aim is not to invent figures but to use the double entry relationships that must hold. Every missing figure is found as a balancing item in an account where the other entries are known, and then tested against something independent. The overlap with entering opening balances is close: both start by establishing the position at a date.

Where do you start?

Start with an opening statement of affairs: a list of the business’s assets and liabilities at the start of the period, valued as reliably as possible. Its balancing figure is opening capital. Sources include last year’s accounts, bank and loan statements at the start date, supplier statements, unpaid customer invoices, a stock estimate and the fixed asset list. ACCA describes opening capital as the starting point for every reconstruction. Then prepare the same list at the period end.

How do control accounts find missing sales and purchases?

A total receivables account works in reverse. If opening and closing debtors and the cash received from customers are known, credit sales are the balancing figure. ACCA’s article notes that if any three of the four figures are known, the fourth can be found. The same applies to purchases using a total payables account, adjusted for discounts, refunds and goods taken by the owner. The mechanics are the same as normal ledger control accounts; the difference is that the control account is being used to calculate a figure rather than to prove one.

Illustration only. Opening debtors are £6,000, closing debtors £8,500, and receipts from customers in the bank statements total £94,000. Credit sales must be £94,000 + £8,500 − £6,000 = £96,500. Cash sales are added separately if takings were not all banked.

How do margin and mark up fill the gaps?

Where a business prices consistently, gross profit relationships can find a missing sales, purchases or closing stock figure. ACCA gives the example of stock destroyed by fire: if the gross profit percentage on sales is known, the trading account gives closing stock as a balancing figure.

Margin and mark up must not be confused. HMRC’s Enquiry Manual at EM3503 sets out the conversions HMRC’s own officers use: gross profit rate equals mark up rate divided by (mark up rate plus 100), times 100; and mark up rate equals gross profit rate divided by (100 minus gross profit rate), times 100. So a 25% mark up on cost is a 20% margin on sales. EM3508 shows HMRC building a weighted mark up from the product mix, and adjusting for wastage, pilferage, price cuts and inexperience before treating any shortfall as omitted takings. If the accounts preparer does the same exercise first, the figures are far easier to defend.

How are cash and drawings reconstructed?

Cash is the weakest point in most incomplete records jobs. Build a cash account: opening cash in hand, add takings not banked, deduct cash expenses, cash banked and cash drawings, and compare with closing cash in hand. ACCA notes that the missing figure in this account is often the owner’s drawings.

That is exactly where HMRC looks. EM3555 says enquiry officers may find that drawings are a balancing figure, and that such a figure can be tested by a personal cash flow analysis; where that test shows the declared figures are insufficient and there is no reasonable explanation, it is realistic to assume the shortfall is extra drawings from the business or undisclosed income. A balancing drawings figure should therefore be checked for credibility against what the owner actually spends on living costs. See capital and drawings accounts for sole traders.

What is the net worth method?

Where records are so poor that sales and expenses cannot be rebuilt, profit can still be measured from the change in net assets. ACCA gives the formula: profit equals closing net assets, less opening net assets, plus drawings, less capital introduced. HMRC’s capital statements rest on the same idea. EM3583 explains that private expenditure plus the increase in total wealth must equal total income, and EM3586 notes that where business capital is included, the change in it, adjusted for living expenses and other personal spending, represents business profits.

Illustration only. A trader’s net business assets were £22,000 at the start of the year and £31,000 at the end. She paid an inheritance of £5,000 into the business and her drawings are estimated at £26,000.

Net worth calculation £
Closing net assets 31,000
Less opening net assets (22,000)
Increase in net assets 9,000
Add drawings 26,000
Less capital introduced (5,000)
Profit for the year 30,000

The weakness is obvious: the result is only as good as the drawings estimate and the asset valuations. HMRC’s own guidance at EM3581 accepts that the accuracy of the private expenditure figure can make the exercise ineffective, while noting that the Court of Appeal has accepted capital statements as a reasonable way to measure income where nothing more reliable exists.

What should the tax return and the client be told?

GOV.UK says that if records are lost, stolen or destroyed and cannot be replaced, the taxpayer must do their best to provide figures and tell HMRC when filing whether they are estimated or provisional. The SA103F notes explain that provisional figures can be used if final figures are not ready by the deadline, with an explanation in box 103 of why, and when final figures will follow. Accounts prepared from incomplete records should say so in the accountant’s report or the notes, and the working papers should show every assumption.

The client also needs to understand that poor records carry their own risk. HMRC’s Enquiry Manual at EM4650 explains that a penalty of up to £3,000 can be charged for each failure to keep or preserve adequate records for a return, although HMRC says it seeks this only in more serious cases. The ongoing duties are summarised in record keeping rules for the self employed.

What mistakes come up most often?

  • Using a single balancing figure for drawings without checking it against the owner’s living costs.
  • Applying a mark up rate as if it were a margin, which overstates or understates sales.
  • Forgetting cash takings that were spent before banking, so sales are built only from bank receipts.
  • Ignoring goods taken for own use, which depress the gross profit rate; see goods taken for own use.
  • Valuing opening and closing assets on different bases, which distorts the net worth result.
  • Treating money introduced from savings, loans or gifts as capital without evidence of its source.
  • Rebuilding the year and then letting the client carry on as before, instead of setting up a cash book for the next period.

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Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.