Self Assessment · CIS subcontractorsLive — Available now

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CIS tax refund and tax return for subcontractors

CIS subcontractors have tax withheld from every payment before they even file. That deduction is only reclaimed through a Self Assessment return — box 38 of the SA103S. ac-co files that return and gives you a labelled estimate of what's owed back, never a promise.

▸ Start your return — £29 See the Self Assessment hub

HMRC-recognised · files through SA100 · estimate, always labelled

What we fill in first

Box 9Turnover (gross, before CIS)

Box 38CIS deductions

Box 21Net profit

Looking for the full CIS product?

Building the full CIS product — PDS capture, deductions register, verify & CIS300.

This page is the Self Assessment filing angle: getting your box 38 claim into HMRC correctly. The wider CIS product — photographing every Payment and Deduction Statement, a running deductions register, contractor verification and monthly CIS300 returns — is on the waitlist.

See the CIS product & join the waitlist →

WHAT WE FILL IN FOR YOU

Your CIS refund claim, box by box.

A CIS refund isn't a separate claim form — it's boxes on the same SA103S every self-employed subcontractor files. Get the gross/net distinction right in box 9 and the deduction in box 38 does the rest.

SA103S · Box 9

Turnover

Your gross pay before CIS was deducted — not the smaller amount that actually landed in your bank account.

Source: What is the Construction Industry Scheme (CIS) — gov.uk

SA103S · Box 20

Total allowable expenses

Materials, tools, travel between sites and the rest — categorised from your bank feed and receipts.

SA103S · Box 21

Net profit

Turnover minus allowable expenses — the profit figure your Income Tax and Class 4 NIC are calculated on.

SA103S · Box 38

CIS deductions

Every 20% (or 30%) a contractor withheld across the year, added up from your Payment and Deduction Statements and offset against what you owe.

Source: CISR12160 — subcontractor's payment and deduction statement — gov.uk (HMRC manual)

WHAT YOU GET

Everything this return files, keeps and tells you.

Files for you

Sent to HMRC, with your deductions claimed back.

SA100 with box 38 filledCIS deductions suffered, claimed back.

Keeps for you

Every statement and every job, gross to net.

Every Payment and Deduction Statement
Gross vs net pay, per job

Tells you

An estimate, labelled as one, until the return is filed.

A labelled refund estimateFrom incomplete data, until it matches your filed return — never a promise.

THREE THINGS PEOPLE GET WRONG

CIS refund claims — the small print that costs money.

Gross

Box 9 is gross turnover, not net pay

Turnover on your SA103S is what you were paid before CIS came off — not the smaller net amount you actually received. Enter the net figure and both your profit and your refund claim come out wrong.

Source: What is the Construction Industry Scheme (CIS) — gov.uk (opens in a new tab)

PDS

A missing statement makes the claim harder to prove

HMRC's own manual treats the Payment and Deduction Statement as the record evidencing what a contractor withheld. Lose a month's PDS and you're reconstructing evidence for that deduction from bank statements instead.

Source: CISR12160 — subcontractor's payment and deduction statement — gov.uk (HMRC manual) (opens in a new tab)

Gross

The MTD ITSA threshold is measured on gross income

Making Tax Digital for Income Tax mandation is tested against your gross qualifying income — before CIS deductions come off. Subcontractors who look under the line net can find they're over it gross.

Source: Find out if and when you need to use Making Tax Digital for Income Tax — gov.uk (opens in a new tab)

No sign-up — try it right here

See what you might be owed — no sign-up.

The same engine that fills box 38 on your SA103S does the sum here.

Fix the figures above to see an estimate.

Estimate only — not tax advice. Figures use published HMRC rates and thresholds for the selected tax year; your actual bill depends on your full return.

An estimate from the figures you enter — not a tax calculation. Your real refund comes from your filed Self Assessment return.

PRICING

One fee per return. No subscription.

A CIS refund claim is one supplementary page — the Simple tier covers it.

50% off until 14 January 2027

Simple

One supplementary page

£29£59/ return

Self-employment plus CIS deductions, nothing else — SA100 plus your SA103S with box 38 filled.

Start a return

Complete

Every income type

£65£129/ return

CIS work plus another income type — a rental property, dividends or capital gains — every supplementary page included.

Start a return

Getting your CIS deductions back, three ways.

A refund agent takes a cut of the money; ac-co reclaims it through your Self Assessment for a fixed fee.

Row	HMRC online	Refund agent	ac-co
Fee	Free	£354, taken from your refund [RIFT Tax Refunds — fees, 2026-09-13]	£99 fixed, or £129 from the refund
Fee is a fixed amount, not a cut of your refund	Yes	No	Yes
Runs a deductions register from your PDS photos	No	Some do	Yes

RIFT's own fee page, read 2026-09-13 — check their current rate.

OBJECTIONS

Before you file.

How much will I get back?

We won't put a number in front of you until you enter your own figures — and even then it's an estimate, not a promise. The calculator uses the same engine that fills your Self Assessment, but your real refund comes from your filed return and HMRC's own calculation.

Is there a separate CIS refund form?

No — CIS deductions are reclaimed through your Self Assessment, box 38 of the SA103S self-employment page, not a standalone claim. Missing the 31 January deadline adds a £100 penalty even if you're due money back.

Why was 20% (or 30%) deducted from my pay?

Contractors must withhold CIS as an advance against your Income Tax and National Insurance — 20% if you're verified with HMRC, 30% if you're not. Gross payment status brings that to 0%.

What if I've lost some of my Payment and Deduction Statements?

You can still claim, but a missing PDS makes the deduction harder to evidence if HMRC asks. Bank statements showing the net payment can help reconstruct the gross and deducted amounts.

Does my CIS work count toward the MTD ITSA threshold?

Yes — the threshold is tested on your gross qualifying income, before CIS deductions are taken off. Check gov.uk's current threshold guidance for where that line sits this year.