HMRC Cash Basis vs Accrual Accounting for UK Sole Traders (2026–27): SA103 Guide

Short answer: Under HMRC’s reformed Self Assessment rules (Finance Act 2024, in force for 2025/26, 2026/27, and 2027/28), the cash basis vs accrual accounting UK rules flipped: Cash Basis is now the automatic default method for every UK sole trader, with no turnover cap, no £500 interest limit, and full sideways loss relief. On Form SA103S or SA103F, you only pay tax on customer invoices actually paid by 5 April—unless you tick Box 8 (SA103S) or Box 14 (SA103F) to opt into Accrual Accounting.

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Before the Finance Act 2024 reforms, millions of UK builders, electricians, plumbers, CIS subcontractors, and freelancers were forced onto traditional accrual accounting—or hit by old Cash Basis restrictions (the £150,000 turnover entry cap, the £300,000 exit cap, the £500 limit on bank/loan interest deductions, and blocked sideways loss relief).

According to HMRC’s Business Income Manual (BIM70000) and Cash Basis guidance, all four of those restrictions have been abolished. Below is the complete 2026–2027 UK sole trader guide to Cash Basis vs Traditional Accrual Accounting, showing how each method treats unpaid March/April invoices, work vans vs cars, CIS 20% deductions, and Making Tax Digital (MTD for ITSA). For related UK guides, see our SA103S and SA103F form guide, UK sole trader allowable expenses list, and UK CIS subcontractor invoice guide.

What changed when HMRC made Cash Basis the default for all UK sole traders?

Starting from the 2024/25 tax year and continuing across 2025/26, 2026/27, and 2027/28, HMRC reversed the default on Self Assessment schedule SA103S and SA103F:

Rule / Threshold	Old Cash Basis Rules (Before Reform)	Current 2026–2027 HMRC Cash Basis Rules (Finance Act 2024)	Traditional Accrual Accounting (Opt-Out Election)
Default Status on SA103S / SA103F	Opt-in election required	Automatic Default for all sole traders & partnerships of individuals	Must tick Box 8 (SA103S) or Box 14 (SA103F) every year to opt out
Turnover Cap to Use the Method	£150,000 entry cap / £300,000 exit cap	No turnover limit (£0 to unlimited)	No turnover limit
When Customer Invoices Are Taxed	When payment is received	Only when payment is actually received (up to 5 April)	When the work is done / invoice is issued, even if the client has not paid you by 5 April!
When Supplier Receipts Are Deducted	When paid	When actually paid (credit card purchase counts on the day of swipe)	When incurred / billed by supplier (requires year-end creditors, debtors, prepayments & stock adjustments)
Business Loan & Overdraft Interest Cap	Capped at £500 per year	£500 cap ABOLISHED — 100% of wholly & exclusively business interest is deductible	100% of wholly & exclusively business interest is deductible
Sideways Loss Relief (Against PAYE / Previous Years)	Restricted under old cash basis	Restriction ABOLISHED — full sideways & early-years loss relief available	Full loss relief available
Work Vans, Tools & Plant (£1,000+ Equipment)	Deducted 100% as an expense when paid (except cars)	Deducted 100% upfront as an allowable expense in the year paid (cars remain excluded)	Claimed via Capital Allowances (AIA / Writing Down Allowances)

Why is Cash Basis vastly better for UK tradespeople and CIS subcontractors in 2026–27?

Consider a UK builder or electrical contractor who issues a £6,500 invoice on 28 March 2026, and the client pays by BACS on 14 April 2026 (after the 5 April end of the UK tax year):

1. Under Traditional Accrual Accounting: Because you completed the work and dated the invoice before 5 April 2026, that £6,500 is taxed in the 2025/26 tax year—even though the cash was not in your bank account on 5 April! You also have to count every roll of cable, bag of plaster, and unbilled work-in-progress on 5 April as closing stock.
2. Under HMRC’s Default Cash Basis: Because the client paid on 14 April 2026, that £6,500 falls into the 2026/27 tax year, pushing the Income Tax and Class 4 National Insurance bill back by 12 full months—and you never have to perform a year-end stocktake or calculate accruals and prepayments.

How CIS 20% Subcontractor Deductions Work Under Cash Basis

If you work under the Construction Industry Scheme (CIS), your Cash Basis turnover is based on the payment dates shown on your monthly CIS Payment and Deduction Statements (PDS) received for payments made up to 5 April:

• You still report the Gross CIS amount (before the 20% CIS deduction) inside your turnover box (SA103S Box 9 / SA103F Box 15), and enter the 20% CIS tax deducted at source in SA103S Box 38 / SA103F Box 81 so HMRC credits it pound-for-pound against your tax bill and Payments on Account.

How do you deduct a work van vs a car under the HMRC Cash Basis?

This is the one equipment rule every UK tradesperson must know before buying a vehicle:

• Work Vans (Ford Transit, Vauxhall Vivaro, Sprinter, or qualifying double-cab pickup treated as a van) & Tools: Under the Cash Basis, the cost of buying a work van, power tools, ladders, testing rigs, or laptops is deducted 100% upfront as a normal allowable capital expense in the tax year you pay for it (adjusted for your business-use percentage). If you buy a van on Hire Purchase (HP), you deduct the capital repayments as you pay each monthly instalment, plus 100% of the business loan interest!
• Cars (Including Estate Cars & SUVs): Cars are the only equipment asset excluded from an immediate Cash Basis expense write-off. For a car used in your sole trader business, you either:
  1. Claim HMRC Simplified Mileage at 45p per mile (first 10,000 business miles) and 25p per mile thereafter (see our UK self-employed mileage allowance guide); or
  2. Claim Capital Allowances (100% First Year Allowance for brand-new zero-emission electric cars, 18% main rate pool for CO2 emissions of 1–50g/km, or 6% special rate pool above 50g/km) plus the business proportion of actual fuel and running costs.

Does Cash Basis work with Making Tax Digital (MTD for ITSA) in April 2026 and April 2027?

Yes—100%. Under HMRC’s Making Tax Digital for Income Tax rules (starting 6 April 2026 for sole traders with qualifying income over £50,000 and 6 April 2027 over £30,000), using the Cash Basis makes your four quarterly updates (5 August, 5 November, 5 February, and 5 May) effortless:

• Each quarterly summary is simply the paid invoices received minus the paid allowable receipts and 45p/25p mileage logged during that quarter—with zero accrual adjustments required.
• And because Keel works 100% without a mandatory Open Banking connection (see UK sole trader bookkeeping apps with no bank link), you don’t need to pay £25–£40/month for Dext + cloud accounting subscriptions or replace limited 3-invoice apps like Invoice Simple. You can import your existing client and invoice history in seconds via the Switch & Import CSV/ZIP App Store Edition.

Who cannot use the HMRC Cash Basis (and when should you tick Box 8 / Box 14 to opt out)?

A small list of businesses remains excluded from the Cash Basis by statute (ITTOIA 2005 s 31C), including limited companies, LLPs, partnerships with a corporate partner, Lloyd’s underwriters, businesses with a current herd basis election, and businesses claiming R&D tax reliefs or creative industry reliefs.

For a normal UK sole trader, you would only tick Box 8 on SA103S (or Box 14 on SA103F) to opt out into Traditional Accrual Accounting if a mortgage broker or commercial tender explicitly requires full accrual balance-sheet accounts showing debtors, creditors, and work-in-progress.

Frequently asked questions

Do I need to tick a box on Form SA103S or SA103F to use the Cash Basis in 2026–2027?

No! Under the Finance Act 2024 reforms, the Cash Basis is the automatic default. On your 2025/26 and 2026/27 SA103S (Box 8) or SA103F (Box 14), you leave the accounting method box blank to use the Cash Basis. You only tick Box 8 or Box 14 if you are electing out of the Cash Basis to use traditional accrual accounting.

What happens if I bought a receipt on my credit card on 3 April 2026 but paid off the credit card bill in May 2026?

Under HMRC’s Cash Basis rules (BIM70035), paying for an allowable business expense with a credit card counts as paid on the date of the credit card transaction (3 April 2026, inside the 2025/26 tax year), because the supplier was paid at that point. You do not wait until you pay off the credit card statement.

How do I switch from Traditional Accounting to the Default Cash Basis without double-counting invoices?

When transitioning from accruals to the Cash Basis, HMRC requires simple transitional adjustments in the first Cash Basis year so no income is taxed twice and no expense is deducted twice: any customer invoice that was already taxed on an accrued basis in last year’s return is excluded when the cash actually arrives this year, and any supplier bill already deducted as a creditor last year is excluded when paid this year.

Can I deduct the full cost of a work van upfront under the HMRC Cash Basis?

Yes. Under the Cash Basis, the purchase cost of a commercial work van, power tools, plant, and machinery is deducted 100% upfront as an allowable business expense in the tax year you pay for it (adjusted for any private-use percentage). Passenger cars are the only vehicles excluded from upfront Cash Basis expensing and must use either 45p/25p simplified mileage or Capital Allowances.

Is there still a £150,000 turnover cap or £500 interest limit on the UK Cash Basis?

No. Both the £150,000 entry / £300,000 exit turnover caps and the £500 limit on business loan and overdraft interest deductions were completely abolished by the Finance Act 2024. Sole traders of any turnover level can now use the Cash Basis and deduct 100% of wholly and exclusively incurred business finance interest.

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