HMRC SA103 Accounting Date: ‘Date Your Books or Accounts Are Made Up To’ & Basis Period Reform Guide (2026/27)

Short answer: When HMRC Self Assessment asks for the date your books or accounts are made up to (Box 8 on SA103S or Box 9 on SA103F), enter 05/04/2026 (or 31/03/2026 if you close your books at the end of March) for the 2025/26 tax return, or 05/04/2027 (31/03/2027) for 2026/27. Under HMRC Basis Period Reform (ITTOIA 2005 section 7A), all UK sole traders are taxed on the tax year basis (6 April to 5 April), and HMRC treats any accounting date from 31 March to 4 April as equivalent to 5 April.

⚡ Instant UK HMRC SA103S / SA103F, 45p/25p Mileage & Sole Trader Invoice Toolkit (£GBP): Estimate your 2026/27 Income Tax, Class 4 National Insurance, and Payments on Account in our Free UK Self-Employed Tax Calculator below (or click 🔗 Embed / CSV Template), save up to 5 Free Saves in your iCloud Web Workspace, read our HMRC Form SA103S & SA103F Box-by-Box Guide, compare the UK Self Assessment SA103 App Store Edition, or Download Keel Free on the App Store (£0/mo UK Sole Trader Edition) (uk-self-assessment).

One of the most searched questions every January as sole traders fill out their online HMRC Self Assessment return is: what do I put for the “date your books or accounts are made up to” on the Self-Employment pages (SA103S / SA103F)?

Before April 2024, a sole trader could pick any year-end date (such as 30 April or 31 December) and be taxed on that accounting year (the current year basis). Following HMRC’s Basis Period Reform (Finance Act 2022 Schedule 1), every unincorporated sole trader and partnership in the UK is now taxed strictly on the Tax Year Basis (6 April to 5 April)—which also aligns directly with Making Tax Digital for Income Tax (MTD for IT) starting 6 April 2026.

Below is the exact box-by-box guide for entering your accounting date on SA103S (Box 8) and SA103F (Boxes 8–9 & Boxes 73.1–73.4), how the 31 March to 5 April equivalence rule works, and how to report 5-year spread transitional profits (2023/24 to 2027/28). For companion UK guides, see Self Assessment for the self-employed and cash basis vs accrual accounting on SA103.

What should you enter for date your books or accounts are made up to on SA103S / SA103F?

Use the table below to enter the exact date in Box 8 of Form SA103S (Short) or Box 9 of Form SA103F (Full):

Your Sole Trader Situation	2025/26 Tax Return (Online deadline: 31 Jan 2027)	2026/27 Tax Return (Online deadline: 31 Jan 2028)	Why HMRC Accepts This Date
Standard Tax Year Bookkeeping (Most UK sole traders & CIS subcontractors)	05/04/2026 (Accounting period: 06/04/2025 to 05/04/2026)	05/04/2027 (Accounting period: 06/04/2026 to 05/04/2027)	Matches the official UK tax year end (5 April) to the day
Calendar-Month Bookkeeping (Closing books at the end of March)	31/03/2026 (Accounting period: 01/04/2025 to 31/03/2026)	31/03/2027 (Accounting period: 01/04/2026 to 31/03/2027)	Under ITTOIA 2005 s 7A, HMRC treats any accounting date from 31 March to 4 April as ending on 5 April (no time-apportionment required)
Started Self-Employment Mid-Year (e.g. started trading on 12 September 2025)	Start date (Box 6): 12/09/2025 · Books made up to (Box 8): 05/04/2026 (or 31/03/2026)	Books made up to (Box 8): 05/04/2027 (or 31/03/2027)	In your first tax year, you report from your actual start date up to 5 April (or 31 March)
Stopped Trading / Closed Sole Trader Business Mid-Year (e.g. ceased on 30 November 2025)	Cessation date (Box 7): 30/11/2025 · Books made up to (Box 8): 30/11/2025	No SA103 required if you did not trade in 2026/27	When you permanently cease trading, your final accounts are made up to your cessation date

Why does HMRC treat 31 March and 5 April as the same date (ITTOIA 2005 s 7A)?

Many sole traders and accountants prefer to run monthly bookkeeping from 1 April to 31 March rather than cutting a month in half on 5 April. Under Section 7A of the Income Tax (Trading and Other Income) Act 2005 (ITTOIA 2005):

• If your accounts are drawn up to 31 March, 1 April, 2 April, 3 April, or 4 April, the profits or losses of those 5 days (1 April – 5 April) are automatically treated as falling into the following tax year’s accounts.
• You do not have to manually split out invoices or expenses dated 1 April – 5 April if your chosen accounting date is 31 March—provided you stay consistent from year to year (1 April 2025 – 31 March 2026, then 1 April 2026 – 31 March 2027).
• Under Making Tax Digital for Income Tax (MTD for IT) (mandatory from 6 April 2026 if your qualifying turnover exceeds £50,000), HMRC explicitly allows you to elect calendar quarters (1 April – 30 June, 1 July – 30 September, 1 October – 31 December, 1 January – 31 March) so your MTD quarterly updates match a 31 March accounting date without changing a single filing deadline (7 August, 7 November, 7 February, 7 May).

What if you keep a non-tax-year accounting date (e.g. 31 December) or have Transitional Profits (Boxes 73.1–73.4)?

While 95%+ of UK sole traders use 5 April or 31 March, two special rules apply on SA103F (Full Self-Employment pages) if you had a different accounting year-end before 2023/24:

1. Continuing with a non-tax-year date (e.g., 31 December):
   • Under the Tax Year Basis, you must use Form SA103F (Full) (you cannot use SA103S Short) and time-apportion two sets of accounts by days (9 months / 275 days of the first set + 3 months / 90 days of the second set) to arrive at your 6 April – 5 April taxable profit. Because the second set of accounts may not be finalised by 31 January, you may have to submit provisional figures and amend your return later—which is why HMRC strongly recommends changing your accounting date to 31 March or 5 April.
2. Spreading Transitional Profits from 2023/24 (SA103F Boxes 73.1 to 73.4):
   • If you had a non-March/April year-end in 2023/24 and deducted your accumulated Overlap Relief during the transition year, any remaining transition profit is automatically spread in equal 20% (1/5th) instalments across 5 tax years (2023/24, 2024/25, 2025/26, 2026/27, and 2027/28).
   • On your 2025/26 and 2026/27 SA103F returns, enter the 20% annual instalment brought forward (or elect to accelerate more of it) in Boxes 73.1 to 73.4. If you cease trading before 2027/28, any remaining unspread transition profit becomes taxable in your final year of trading.

How to keep your 6 April – 5 April SA103 ledger clean all year

With Keel (£0/mo Core on iPhone & iCloud Web Workspace), your UK tax year is pre-configured to 6 April – 5 April out of the box—automatically grouping your sole trader invoices, SA103S Box 11–19 allowable expense receipts, 45p/25p mileage logs, and 20% CIS subcontractor statements into a 5-year HMRC audit pack with no Open Banking connection required.

Step-by-step checklist before submitting Box 8 (SA103S) or Box 9 (SA103F)

1. Confirm whether your bookkeeping runs to 05/04/2026 (exact tax year) or 31/03/2026 (calendar-month end under ITTOIA 2005 s 7A).
2. Check Box 10 (SA103S) if you use the default Cash Basis (leave it unticked; only tick Box 10 if you elected traditional accrual accounting).
3. Verify that all invoices and expenses fall within your 12-month period and save your 5-year record pack.

Frequently asked questions

What do I put for “date your books or accounts are made up to” on my HMRC Self Assessment return?

For the 2025/26 UK tax year (6 April 2025 to 5 April 2026), enter 05/04/2026 in Box 8 of SA103S (or Box 9 of SA103F) if you run your books on the standard tax year, or 31/03/2026 if you close your books at the end of March. For the 2026/27 tax year, enter 05/04/2027 (or 31/03/2027).

What if I started being self-employed halfway through the tax year?

Enter the exact date you started trading in Box 6 (If your business started after 5 April...), and still enter 05/04/2026 (or 31/03/2026) as the date your books or accounts are made up to in Box 8. Your turnover and expenses on that first return cover the period from your start date to 5 April (or 31 March).

Does it matter whether I choose 31 March or 5 April as my accounting date?

For HMRC tax purposes, both dates are treated identically. Under section 7A of ITTOIA 2005, HMRC treats any accounting date between 31 March and 4 April as ending on 5 April, so you never have to apportion the 5 days between 1 April and 5 April so long as you use the same date consistently each year.

Can I still have a 30 April or 31 December year-end as a UK sole trader?

Technically you can still draw up internal accounts to another date, but under HMRC’s Basis Period Reform, you are taxed strictly on the profits arising in the tax year (6 April to 5 April). Using any date outside 31 March – 5 April forces you to file the full SA103F pages and time-apportion two accounting periods every single year.

What happened to Overlap Relief on Form SA103?

Under Basis Period Reform, all existing Overlap Relief had to be claimed in the 2023/24 transitional tax year (or via an amendment to the 2023/24 return). From 2024/25 through 2027/28, sole traders who generated net transitional profits in 2023/24 simply report their annual 20% (1/5th) spread transition profit in Boxes 73.1–73.4 of SA103F.

---

This guide is general information based on HMRC Self Assessment (SA103S Notes / SA103F Notes) and the Income Tax (Trading and Other Income) Act 2005 (s 7A) for the 2025/26 and 2026/27 tax years, and is not personal tax advice. Check gov.uk or speak to a qualified UK accountant.