If you're a CIS subcontractor working as a sole trader, your CIS deductions go on the self-employment pages of your Self Assessment return, in one box near the end. Your pay goes in the turnover box near the start, before any deductions. This guide gives the exact box numbers and labels from HMRC's 2025–26 forms and notes (the "2026" versions, for the tax year 6 April 2025 to 5 April 2026), plus the partnership pages.
Adding up the two figures is a separate job. Our guide How to add up your CIS deductions for your tax return covers that.
The short answer
| You fill in | Pay before deductions | CIS deductions |
|---|---|---|
| Self-employment (short), SA103S | Box 9, "Your turnover" | Box 38, "Total Construction Industry Scheme (CIS) deductions taken from your payments by contractors – CIS subcontractors only" |
| Self-employment (full), SA103F | Box 15, "Your turnover" | Box 81, same label |
| Partnership (short), SA104S | Your share of profit (from the Partnership Statement) | Box 30, "Your share of Construction Industry Scheme deductions made by contractors – from box 24 on the Partnership Statement" |
| Partnership (full), SA104F | Your share of profit (from the Partnership Statement) | Box 78, "Share of Construction Industry Scheme (CIS) deductions made by contractors – from box 24 on the Partnership Statement" |
GOV.UK's pay tax and claim back deductions page puts it in plain words. You record "your total pay before deductions were taken, as 'income'" and "the total deductions contractors have taken, as 'CIS deductions'".
Short pages or full pages?
The main return (SA100) asks on page TR 2: "Do you need to fill in the 'Self-employment' pages?" There's a separate page "for each business".
HMRC's SA103S notes say to use the short pages if your turnover was less than £90,000 (or would have been, over a full year). You need the full pages if, among other things:
- your business is more complicated, or turnover was £90,000 or more
- your accounting period ended before 31 March 2026, wasn't 12 months long, or didn't end in the tax year
- you need to adjust profits chargeable to Class 4 National Insurance
The CIS box works the same way on both. Only the number changes.
Self-employment (short): boxes 9 and 38
Box 9, "Your turnover". The notes say to put "the total amount of income received (cash basis) or earned (traditional accounting) by your business before taking off any expenses". For CIS they add: "If you're a subcontractor, make sure you include the full amount for the accounting period (before any Construction Industry Scheme (CIS) deductions made by contractors)."
Box 38, CIS deductions. The notes say: "add up all the deductions made by contractors from 6 April 2025 to 5 April 2026. Use the statements that contractors gave you." They also say: "Do not send these with your tax return." Keep them, though. GOV.UK says HMRC might ask for evidence of your deductions.
The notes word the two boxes differently. Box 9 covers your accounting period, and box 7 asks the date your books are made up to ("between 31 March and 5 April 2026, or the final date of trading"). Box 38 covers the tax year, 6 April to 5 April. If your accounts run to 5 April, the two match. If they run to 31 March, they differ by a few days at each end of the year.
Small earners. Turnover of £1,000 or less doesn't always need reporting. But the notes say if "you're a subcontractor and want to claim back tax deducted under the Construction Industry Scheme (CIS), complete boxes 1 to 8 and box 38".
Self-employment (full): boxes 15, 81 and 82
The SA103F notes repeat the same rules:
- Box 15, "Your turnover": include "the full amount (before Construction Industry Scheme (CIS) deductions made by contractors) for your accounting period".
- Box 81, CIS deductions: "add up all the deductions made by contractors from 6 April 2025 to 5 April 2026".
- Box 82, "Other tax taken off trading income": "If you have had any other tax taken off (not CIS deductions), put the amount in box 82."
One box to watch: box 18. On the full pages, box 18 is "Construction industry – payments to subcontractors". The notes say it "includes the total payments you made to subcontractors". It's a business expense for people who pay subcontractors. It isn't where deductions taken from your own pay go. Those go in box 81.
Partnership pages: box 30 or box 78
If you're a partner, your share comes from the Partnership Statement in the partnership's own return. The SA104S notes say to copy "box 24 figure to box 30" and "box 24A figure to box 31". Box 31 is tax taken off trading income that isn't contractor deductions. On the full partnership pages, the notes say to copy the box 24 figure to box 78.
If you've already had a CIS refund this year
GOV.UK says a sole trader who stops trading may be able to claim back that year's deductions early, on form CIS40 (or CIS41 for partners). The notes cover this. "Even if you've already claimed a CIS repayment, put the deductions in box 38." And: "If you've received a refund of CIS deductions, make sure you include it in box 1 'Tax refunded or set off' on page TR 6 of your tax return." Box 81 on the full pages works the same way.
What HMRC does with box 38
HMRC's tax calculation summary notes (SA110) show the working. Box 38 on the short pages, or boxes 81 and 82 on the full pages, go into "Total tax taken off at source". That total is then taken off your Income Tax, Class 2 and Class 4 National Insurance for the year.
If you file online, you don't do this sum yourself. The SA100 says "if you file online, we'll do the calculation for you". HMRC's manual (SALF303) says the online service "will calculate the tax and the following year's payments on account automatically". Our guide CIS payments on account explains how the deductions feed into those.
The online return
GOV.UK says 97% of people file online. It doesn't publish the online return's screens, so we haven't described them. It does say what to record: pay before deductions as "income", and the deductions as "CIS deductions". The figures are the same however you file.
Worked example (made-up figures)
Alex is a sole trader. Every figure here is invented. Alex's accounts run to 5 April, use the cash basis and show turnover well under £90,000, so the short pages apply.
| From Alex's records for 2025–26 | Amount |
|---|---|
| Gross pay on CIS statements, two contractors | £30,000 |
| Paid by householders (no CIS, no statements) | £2,000 |
| CIS deductions on the statements | £5,200 |
Following HMRC's notes, box 9 holds all the business income before expenses and before deductions: £32,000. Box 38 holds the deductions from the statements: £5,200. The householder work had nothing deducted, so it adds to box 9 but not to box 38. Expenses go in boxes 11 to 20, which the notes cover separately. What Alex can claim there is a question for HMRC or an accountant.
FAQ
Do I put my net pay (after deductions) in turnover? No. Both sets of notes say to include the full amount before CIS deductions.
Is there a separate CIS page? No. The CIS box sits on the self-employment or partnership pages, under "Losses, Class 2 and Class 4 National Insurance contributions (NICs) and CIS deductions" (short) or "CIS deductions and tax taken off" (full).
Some statements are missing. Can I leave the box blank? The notes point to GOV.UK's pay tax and claim back deductions page. Our guide Is there a CIS end-of-year statement? covers what to do if a contractor won't send them.
I work through my own limited company. Which box? None of these. GOV.UK says a company uses its payroll scheme (the Employer Payment Summary) instead.
Getting the box 38 figure
Box 38 is the total of every deduction on every statement for the tax year. cissplit reads your statements (PDFs or photos) and checks the deduction rate on each one. It flags gaps between a contractor's months, then totals the tax year, with every statement listed by contractor and tax month. Your first 3 statements are free, with no sign-up. It doesn't fill in or send your return, and you still check the figures against your statements.
This isn't tax advice. Check GOV.UK's CIS guidance for subcontractors or an accountant for your situation, and check the figures before you submit anything.