SELF ASSESSMENT: MAIN RETURN, ADDITIONAL INFORMATION & TAX CALCULATION
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Self Assessment return & Tax Calculation
These forms make up the Self Assessment return for an individual for the 2026-27 tax year. SA100 is the main return; SA101 is a supplementary page for additional information that does not fit on the main pages; and SA110 lets a taxpayer on a paper return calculate their own liability. The supplementary pages needed depend on the taxpayer’s income and circumstances.
SA100 Self Assessment Tax Return 2026 (main return)
Purpose
The SA100 is the main Self Assessment tax return for an individual. It allows HMRC to calculate the Income Tax, Capital Gains Tax and National Insurance contributions due for the tax year 6 April 2026 to 5 April 2026. It records personal details, shows which supplementary pages are needed, and collects the simpler kinds of income (interest, dividends, pensions and state benefits), the main tax reliefs (pension payments, Gift Aid, Blind Person's Allowance), student loan and Child Benefit charges and the Marriage.
Deadlines
For the 2026-27 tax year the return must be received by 31 October 2027 on paper, or by 31 January 2028 if filed online, or three months after the notice date if that is later. The tax balance and the first payment on account for 2026-27 are also due on 31 January 2028, and the second payment on account is due on 31 July 2028. A late return carries a £100 To have a tax underpayment of under £3,000 collected through the tax code, the return must be in by 31 October (paper) or 30 December 2027 (online).
Requirements
The taxpayer needs the UTR, National Insurance number and, if applicable, the employer reference, plus all the documents for income and gains in the year: P60 or P45, bank and building society interest certificates, dividend vouchers, pension statements, State Pension and benefit statements, records of pension contributions, Gift Aid records, student loan statements, Child Benefit amounts and, for refunds, bank details. For any extra income types the supplementary pages (SA101 to SA109) must be obtained from gov.uk. Anyone who needs to file must have registered for Self Assessment by 5 October after the end of the tax year, and online filers need a Government Gateway account.
Filing Process
Page TR 1 asks for the date of birth (box 1), name and address if different from the front (box 2), phone number (box 3) and National Insurance number (box 4). Page TR 2 asks nine yes or no questions to decide which supplementary pages are needed: Employment (SA102), Self-employment (SA103), Partnership (SA104), UK property (SA105), Foreign (SA106), Trusts, Capital Gains Tax (SA108), Residence and foreign income and gains (SA109) and Additional information (SA101). For each "Yes", the number of pages should be entered and the correct pages added to the return. Page TR 3 contains the income section. Enter taxed UK interest (box 1), untaxed UK interest (box 2), untaxed foreign interest up to £2,000 (box 3), dividends from UK companies (box 4), other dividends (box 5) and foreign dividends (boxes 6 and 7). Then state the State Pension (box 8), other pensions with tax taken off (boxes 11 and 12), taxable benefits (boxes 13 to 16) and other taxable income with allowable expenses (boxes 17 to 19), pre-owned asset benefits (box 20) and a description (box 21). Page TR 4 covers tax reliefs: payments to registered pension schemes (boxes 1 to 4), Gift Aid payments (boxes 5 to 10) and Blind Person's Allowance (boxes 13 to 16). Page TR 5 deals with Student Loan and Postgraduate Loan repayments, the High Income Child Benefit Charge (total Child Benefit, number of children, stop date), the Marriage Allowance (spouse's name, NINO, date of birth and date of marriage) and the Winter Fuel Payment charge. Paper returns use whole pounds, with income rounded down and expenses and tax paid rounded up.
SA101 Additional Information 2026
Purpose
The SA101 is a supplementary page to the Self Assessment return for less common types of income, deductions, reliefs and other information that do not fit on the main SA100 pages. It collects items such as interest from gilts, life insurance policy gains, stock dividends, close company loans written off, post-cessation business receipts, share scheme income, lump sums and redundancy payments above the exemption, foreign earnings and overseas reliefs, Venture Capital Trust and EIS relief, annual payments.
Deadlines
The SA101 is part of the Self Assessment return, so the same deadlines apply: 31 October 2027 for a paper return and 31 January 2028 for an online return for the 2026-27 year. The balancing payment is due on 31 January 2028. Reliefs such as EIS carry-back or later-year trade loss claims have their own time limits set out in the notes, but the claim is normally made within the normal return window or by an amendment within 12 months of the filing deadline.
Requirements
The taxpayer should hold the broker or bank statement for gilts, the life insurance policy chargeable event certificates, the share scheme certificates and employer statements, the termination or redundancy documents, EIS3 or VCT certificates, pension annual allowance statements from the pension scheme, details of the loans written off by a close company and, where relevant, the HMRC scheme reference number for a disclosed tax avoidance scheme. The correct figures must be rounded in whole pounds, and only sections that apply need to be filled in. The page must be enclosed with the SA100 and the "supplementary pages" box (box 21 on page TR 8) ticked.
Filing Process
Enter your name and UTR at the top of the first page. Page Ai 1 starts with "Other UK income": gilt interest after tax (box 1), tax taken off (box 2) and the gross amount (box 3). Life insurance gains are recorded in boxes 4 to 11, giving the amount of the gain, the number of years the policy was held and any deficiency relief. Then record stock dividends (box 12), bonus issues (box 13), close company loans written off or released (box 13.1) and post-cessation business receipts (boxes 14 and 15, with the tax year in which the income is to be taxed). Page Ai 2 covers share schemes (box 1), lump sums and certain post-employment income (box 3), Employer Financed Retirement Benefit Scheme lump sums (box 4), redundancy and compensation above the £30,000 exemption (box 5), tax taken off (box 6) and deductions such as the compensation exemption (box 9), Seafarers' Earnings Deduction (box 11), foreign earnings not taxable in the UK (box 12) and UK patent royalties paid (box 15). Its "Other tax reliefs" part claims relief for subscriptions to Venture Capital Trusts (box 1), the Enterprise Investment Scheme (box 2), Community Investment Tax Relief (box 3), annual payments (box 4), qualifying loan interest (box 5), post-cessation trade relief (box 6) and Seed EIS (box 10). Page Ai 3 covers earlier years' losses (boxes 1 and 2), relief for later-year trade losses (boxes 3 to 5), payroll giving (box 6) and the Married Couple's Allowance (boxes 1 to 11). Page Ai 4 deals with pension savings tax charges (boxes 10 to 20): the amount saved above the Annual Allowance, scheme tax paid, overseas transfer charges, unauthorised payments, and the scheme or promoter reference number and tax year for any disclosed tax avoidance scheme.
SA110 Tax Calculation Summary 2026
Purpose
The SA110 lets a taxpayer on a paper return calculate their own Self Assessment liability. It shows total tax, student loans, National Insurance and Capital Gains Tax due or overpaid, any underpaid tax collected through PAYE codes, and the payments on account for the next tax year.
Deadlines
If a paper return arrives by 31 October 2027, HMRC can calculate the tax for you; online returns are calculated automatically. Tax is due 31 January 2028, with payments on account on 31 January 2028 and 31 July 2028.
Requirements
The completed SA100 and supplementary pages, the SA110 notes and working sheet, P2 coding notice, P60 and tax paid records.
Filing Process
Page TC1: use the notes working sheet to work out the figures. Box 1 is total tax (which may include student and postgraduate loan repayments), Class 2 and Class 4 NICs due before payments on account; box 2 is the same total if overpaid. Then show the parts: box 3 Student Loan repayment, 3.1 Postgraduate Loan repayment, 4 Class 4 NICs, 4.1 Class 2 NICs, 5 Capital Gains Tax and 6 pension charges. Underpaid tax: box 7 earlier years in your 2026-27 tax code, box 8 2026-27 underpayment in your 2026-27 code and box 9 outstanding debt in your code (from the P2 coding notice). Payments on account: tick box 10 if you are reducing 2026-27 payments and enter the reduced first payment in box 11 (with pence), explaining why in box 17. Page TC2: box 12 blind person's surplus allowance and 13 married couple's surplus allowance transferred from a spouse; box 14 increase and 15 decrease in tax because of adjustments to an earlier year (for example averaging); box 16 any 2026-27 repayment claimed now (such as a loss carry-back); box 17 any other information.