Since April 2024, cash basis is the default accounting method for sole traders — meaning you record income when received and expenses when paid, which is how most people naturally track their money anyway. Here is what this means for your Self Assessment return in 2026/27.
Cash Basis vs Traditional (Accruals) Accounting
| Feature | Cash basis | Traditional accruals |
|---|---|---|
| Record income | When cash received | When invoice issued |
| Record expenses | When cash paid | When invoice received |
| Year-end debtors | Not in taxable profit | Included in taxable profit |
| Year-end creditors | Not deductible yet | Deducted from profit |
| Capital purchases | Deduct in full immediately | Use AIA/WDA rules |
| Car costs | Mileage rate only (45p/mile) | Can use actual costs + capital allowances |
| Interest on loans | Cap of £500/year | No cap |
| Default since | April 2024 | Must opt out to use |
Who Uses Cash Basis (The Default)
Cash basis is now the default for all sole traders and partnerships that are not incorporated. You use it automatically unless you opt out on your Self Assessment return (SA103 box 8).
You must opt out of cash basis if you are:
- A Lloyd’s underwriter
- Using averaging for farm profits or creative artists
- A limited liability partnership (LLP)
- Finding that the £500 interest cap is too restrictive (e.g. heavily financed businesses)
You may prefer to opt out if:
- You want to carry losses back more flexibly (traditional accounting offers wider loss relief options)
- You have significant capital expenditure that you want to plan through capital allowances
- Your accountant prepares statutory accounts on the accruals basis
How Cash Basis Works in Practice
Example: James is a freelance web developer. His tax year runs 6 April 2026 – 5 April 2027.
In March 2027 he invoices a client £5,000 for a project. The client pays in May 2027. Under cash basis, that £5,000 is income for 2027/28 (when the cash arrived) — not 2026/27.
In January 2027 he buys a new laptop for £1,200. He pays the bill immediately. Under cash basis, the full £1,200 is deductible in 2026/27 — no capital allowance calculation needed.
This simplicity — income in when cash in, expense out when cash out — is why cash basis suits most small self-employed people.
Capital Purchases Under Cash Basis
One of the biggest simplifications under cash basis is capital expenditure. Under traditional accounting, buying a business asset (equipment, furniture, tools) requires you to apply the Annual Investment Allowance (AIA) or Writing Down Allowance (WDA) rules. Under cash basis, you simply deduct the cost in the year you pay it.
| Asset type | Cash basis treatment | Traditional treatment |
|---|---|---|
| Laptop, equipment, tools | Deduct full cost in year of purchase | AIA (100%) or WDA (18%) |
| Office furniture | Deduct full cost | AIA or WDA |
| Car | Cannot deduct purchase price — use mileage rate | Capital allowances + actual running costs |
| Property | Cannot deduct — must use traditional accounting | Capital allowances |
The exception is a car: under cash basis you cannot deduct the cost of buying a car. Instead, you claim the HMRC approved mileage rate of 45p per mile (first 10,000 miles) and 25p thereafter for business use.
Key Figures 2026/27
| Amount | |
|---|---|
| HMRC mileage rate (first 10,000 miles) | 45p per mile |
| HMRC mileage rate (above 10,000 miles) | 25p per mile |
| Motorcycle rate | 24p per mile |
| Bicycle rate | 20p per mile |
| Interest deduction cap under cash basis | £500/year |
| Turnover limit for cash basis | No limit (since April 2024) |
| Trading allowance (no expenses needed) | £1,000/year |
Losses Under Cash Basis
Under cash basis, losses can be:
- Carried forward to offset against future trading profits from the same trade
- Set against other income in the same year, but only if the loss arises from certain activities
Cash basis restricts some of the loss relief options available under traditional accounting. If you regularly make losses and want to offset them against employment income or other sources, traditional accounting may give you more flexibility.
How to Opt Out of Cash Basis
If you prefer to use traditional (accruals) accounting, opt out on your Self Assessment return. On the SA103 (Self-Employment) supplementary page, tick box 8 (“If you used the cash basis to calculate your income and expenses, put ‘X’ in the box”). Leaving this box blank means you are using cash basis.
To opt out: leave box 8 blank does not opt you out — you need to tick it to confirm cash basis, and not ticking it means you are choosing traditional accounting. Check HMRC’s current SA103 notes for the precise instruction for the year you are filing.
See our Self Assessment guide, PAYE expenses guide, and self-employed expenses guide.