Accounting for a Sole Trader: The Mortgage Problem

A mortgage broker in Manchester tells this story often. A plumber, turning over £68,000 a year, applies for a £220,000 mortgage. Good income, steady work, eight years self-employed. The lender asks for three years of certified accounts. The plumber has SA302 forms from HMRC and a spreadsheet. The lender says no.

That rejection is not unusual. It is the natural consequence of treating accounting for a sole trader as a chore done once a year to keep HMRC satisfied, rather than as a record that serves three different audiences simultaneously. One of those audiences can cost you a house.

The plumber's problem is not that he earns too little. It is that eight years of self-employment produced eight years of minimal records: bank statements, a rough spreadsheet, and the number HMRC accepted. Lenders want more. And from April 2026, HMRC will too.

The Three Audiences Your Records Must Satisfy

Most sole traders think about accounting in one direction: towards HMRC. Keep records, file a Self Assessment return by 31 January, pay what you owe. That is the legal minimum. It is not sufficient.

Accounting for a sole trader in 2026 has three audiences, and each one wants something slightly different.

HMRC

HMRC wants your taxable profit: total income minus allowable expenses. It accepts a range of accounting methods, including cash basis (money actually received and paid) and traditional accruals (money earned and incurred, regardless of when it moves). It will open an enquiry into roughly 300,000 Self Assessment returns each year, according to HMRC's own published figures, and when it does, it wants to see the original records behind the numbers: sales invoices, purchase receipts, bank statements, mileage logs.

HMRC's requirements are the floor, not the ceiling.

Mortgage lenders

Lenders want your sustainable income. They typically require two to three years of certified accounts or, at minimum, SA302 tax calculation forms accompanied by the full Tax Year Overview from HMRC's portal. Many high-street lenders will also ask for the accounts themselves, not just the tax summary. They calculate affordability on your net profit after expenses, not your turnover, which is the figure sole traders tend to quote when anyone asks how much they earn.

A sole trader turning over £68,000 with £22,000 in legitimate business expenses is a £46,000-a-year earner to a mortgage underwriter. That distinction matters enormously when calculating how much you can borrow.

You

You need to know whether your business is actually making money. This sounds obvious. It is not. A sole trader who invoices aggressively but tracks expenses loosely can easily miscalculate net profit by thousands of pounds per year. A tool bought on a personal card and never claimed, a subcontractor payment forgotten when calculating profit, fuel receipts that did not make it into the spreadsheet: each is small individually. Compounded over several years, they add up to a materially wrong picture of business performance.

Good accounting for a sole trader does not just satisfy external demands. It tells you whether to take on that big contract, whether you can afford an apprentice, whether the business is growing or slowly shrinking.

The Cash Basis Trap That Costs Sole Traders a Mortgage

When HMRC introduced cash basis accounting for sole traders in 2013, it was marketed as a simplification. Record what comes in, record what goes out, file the difference. No complicated accruals calculations, no work-in-progress adjustments, no need to account for invoices that have not yet been paid.

For a tradesperson with straightforward finances, cash basis is genuinely simpler. But it creates a specific problem at the moment accounting for a sole trader matters most: the mortgage application.

Here is why. Under cash basis, if you invoice a customer in March 2025 but they pay in April 2025, that income does not appear in your 2024-25 accounts. It lands in 2025-26. If you had a strong end-of-year push, as many sole traders do, your reported profit can look significantly lower than your actual earnings. Lenders lend against the reported figure.

This is not a hypothetical. A self-employed electrician completing a £15,000 commercial job in late March 2026, with payment due in 30 days, would show that income in their 2026-27 accounts. Their 2025-26 return shows the year without it. If they apply for a mortgage in mid-2026, that £15,000 job, which they genuinely earned, is invisible to the lender.

Traditional accruals accounting records that income in the year the work was done, not the year the invoice was paid. It is more complex to maintain. It is also more accurate as a representation of your business income, which is what lenders are actually trying to measure.

If you are planning a mortgage application in the next two to three years, the choice of accounting method is a structural decision that reaches well beyond your January tax return. This is the kind of consideration that software comparison articles rarely raise, because accounting software will usually default to cash basis without flagging the downstream consequences.

What HMRC's MTD Actually Changes for Sole Traders

From April 2026, sole traders earning above £50,000 must file quarterly updates to HMRC under Making Tax Digital for Income Tax Self Assessment. From April 2027, the threshold drops to £30,000. Those earning above £20,000 follow in April 2028.

This is frequently discussed as a compliance burden, and the software questions it raises are real. But MTD changes something more fundamental about accounting for a sole trader: it forces the creation of a running record, built throughout the year rather than assembled in January.

Under the current Self Assessment system, a sole trader can technically reconstruct their records at year end. Many do exactly this: gather bank statements in December, allocate everything to categories, file by 31 January. The records exist, technically, but they are assembled retrospectively, often under pressure, and often incomplete.

MTD quarterly submissions require you to report income and expense totals four times a year, plus a final declaration. This cannot be done retrospectively without significant pain. The software must connect to live records: bank feeds, digital receipts, categorised transactions. Which means sole traders above the threshold will, for the first time, accumulate a quarterly accounting record as a natural byproduct of compliance.

That quarterly record is exactly what a mortgage lender wants to see. It is also what HMRC wants in an enquiry. And it is what you need to understand your own business in something closer to real time rather than twelve months after the fact.

The practical question of whether to handle this yourself or use an accountant is real and worth resolving before April 2026. But the record itself is no longer optional above the threshold.

The Records You Actually Need to Keep

HMRC requires sole traders to keep records for at least five years from the 31 January submission deadline for the relevant tax year. A 2024-25 return filed in January 2026 requires records kept until at least January 2031.

The records HMRC can request during an enquiry include:

Income records: sales invoices, receipts from customers, bank statements showing deposits, any records of cash received.

Expense records: purchase receipts, supplier invoices, bank statements showing payments, mileage logs for business travel, records of assets purchased (vehicles, tools, equipment).

Subcontractor and payroll records: if you operate under CIS (Construction Industry Scheme), deduction statements, payment records, and monthly returns.

Capital records: assets bought or sold that attract capital allowances, including the original purchase cost and any disposal proceeds.

The five-year retention requirement is a legal minimum. For mortgage purposes, lenders typically want two to three years, sometimes going back further for larger loans. For an HMRC enquiry that suspects significant errors, the investigation window can extend to six years for careless errors and twenty years for deliberate ones.

A spreadsheet can technically satisfy HMRC's requirements. So can a shoebox of receipts, scanned or physical. But neither survives an enquiry with any ease, and neither gives a mortgage lender confidence. The data migration problem that catches sole traders when they switch accounting software is partly this: historical records are hard to move and even harder to reconstruct cleanly when you need them to look credible to a third party.

Why Optimising Only for HMRC Comes Back Around

The plumber in Manchester did not fail the mortgage application because he was dishonest or disorganised by any ordinary measure. He failed because he optimised accounting for a sole trader in one direction: keeping HMRC satisfied at minimum cost and effort.

That is a rational response to the incentives in place under Self Assessment. The system accepted reconstructed January records. HMRC processed them. No penalty arrived. No warning came.

What the system did not do was tell him that a mortgage lender would want certified accounts from a qualified accountant, not a tax summary from HMRC's own portal. It did not tell him that his cash basis elections would mean a strong March would be invisible to an underwriter in April. It did not tell him that accounting for a sole trader serves audiences beyond HMRC, and that failing those audiences has costs HMRC will never warn you about.

His story ends reasonably well. He found a specialist self-employed mortgage broker, worked with a traditional accountant to certify two years of reconstructed accounts, and bought the house eighteen months later than planned. The delay cost him, in a rising market, somewhere in the region of £15,000 in additional purchase price. Proper accounting for a sole trader would not have cost that much in total over the same period.

From April 2026, MTD closes one gap. Quarterly submissions will mean the records exist digitally throughout the year. They will not automatically be certified by a qualified accountant. They will not automatically be on accruals. They will not automatically satisfy every lender's specific requirements.

But they are a start. And for sole traders above the threshold, they are mandatory. The software you choose now will determine whether those mandatory records are also useful, or merely compliant.

The One Thing to Do Before April 2026

If you are earning above £50,000 and not already using software that connects to your bank account and captures transactions throughout the year, April 2026 is now eight months away. The first MTD quarterly submission deadline for 2026-27 will arrive in August 2026.

Start with your records. Not your software subscription, not your accountant's invoice. The actual invoices you issued in the last twelve months. If they are in a folder on your phone, that is a start. If they are on paper in a van glovebox, today is a good day to photograph them and file them somewhere searchable.

If a mortgage application is in your next three years, talk to an accountant now, not in January, about whether cash basis is serving you. The year-two trap that catches many sole traders with accounting software is often this: defaults set up in year one, never revisited, shaping a financial record that works for HMRC but nowhere else.

Accounting for a sole trader has always served more than one master. From April 2026, it will be harder to pretend otherwise.