Self Assessment July 31 Deadline: Complete Guide for CIS Returns Clients
The Self Assessment July 31 deadline is the date your second payment on account is due to HMRC, normally half of last year's bill. If you also work under the Construction Industry Scheme (CIS), the tax already deducted by contractors can shrink or even remove those payments.
Published 3 October 2026 · Updated 3 October 2026
The Self Assessment July 31 deadline is when your second payment on account falls due, and for most people it is half of last year's tax bill. If you also work as a subcontractor under the Construction Industry Scheme (CIS), the tax contractors have already deducted can cut those payments sharply, or switch them off altogether.
Many drivers and couriers pick up CIS work on the side, such as site deliveries, labouring or van work for a contractor. That mix makes the 31 July payment harder to predict than it looks. This guide explains how the payment is worked out, how your CIS deductions interact with it, and when it is sensible to ask HMRC to reduce it.
We keep the focus on the July payment mechanics. For the basics of CIS itself, read our CIS returns FAQ for drivers, and for a full calendar see key tax dates for Uber drivers.
Key takeaways
- The 31 July payment is your second payment on account, normally half of last year's Self Assessment bill including Class 4 National Insurance.
- You skip payments on account if last year's bill was under £1,000, or if more than 80% of your tax was paid outside Self Assessment, which includes CIS deductions.
- CIS deductions are advance payments of tax and National Insurance, so a bigger CIS year usually means smaller payments on account.
- You can ask HMRC to reduce payments on account if you expect a lower bill, but you must work out the figure and interest applies if you cut too far.
- Always check your HMRC online account for the exact amount before you pay.
What is the Self Assessment July 31 deadline?
The Self Assessment July 31 deadline is the due date for your second payment on account, an advance instalment towards your next tax bill. According to HMRC's guidance on payments on account, instalments fall due on 31 January and 31 July, and each is usually half of the tax you owed last year.
The point of the system is to spread your tax across the year rather than leave one large bill. If your profits stay level, the two payments on account plus any CIS deductions should cover most of your bill when the tax year ends.
How do payments on account work?
Payments on account are two advance payments, due on 31 January and 31 July, each worth about half of the tax you owed for the previous tax year. They are based on last year's figures, not this year's income. Any difference is settled in a balancing payment the following 31 January.
Take a driver whose 2025/26 bill is calculated after they file. The first payment on account towards 2026/27 is due on 31 January 2027. The second is due on 31 July 2027. The balancing payment for 2026/27, plus the first payment towards 2027/28, is then due on 31 January 2028.
| Date | What is due | What it is based on |
|---|---|---|
| 31 January 2027 | Balancing payment for 2025/26 plus first payment on account for 2026/27 | Your 2025/26 return and last year's bill |
| 31 July 2027 | Second payment on account for 2026/27 | The same 2025/26 bill, split in half |
| 31 January 2028 | Balancing payment for 2026/27 plus first payment on account for 2027/28 | Your 2026/27 return |
Class 4 National Insurance is included. The same GOV.UK page says your payments on account cover your next tax bill, including Class 4 National Insurance if you are self-employed. Capital Gains Tax and student loan repayments are dealt with in the balancing payment instead.
Who has to make a payment on account?
You make payments on account when your last Self Assessment bill was £1,000 or more and you paid less than 80% of your tax outside Self Assessment. If either test fails, HMRC does not ask for them. Both conditions are set out in HMRC's guidance, so check the current wording on GOV.UK.
The two tests are separate, and the second one is where CIS matters. Tax outside Self Assessment includes tax collected through your PAYE tax code and, for subcontractors, tax deducted by contractors under CIS.
The £1,000 test
If your bill for the last tax year was under £1,000, HMRC does not ask you to make payments on account. A part-time driver with small profits often falls into this group. You then pay everything in one go on 31 January.
The 80% test
If more than 80% of your tax was collected at source, you are also exempt. A driver with a day job on PAYE and a little self-employed income may pass this test. A subcontractor whose CIS deductions cover most of their liability can pass it too.
How does CIS change the 31 July payment?
CIS deductions change the 31 July payment because they count as tax you have already paid. HMRC's guidance for subcontractors says these deductions count as advance payments towards your tax and National Insurance bill. A larger deduction total leaves a smaller balance, so your payments on account usually fall.
Under the scheme, a contractor must deduct 20% from payments to a registered subcontractor and 30% if you are not registered, according to HMRC's guidance for CIS subcontractors. Those amounts are reported to HMRC, and you claim credit for them through your Self Assessment return.
Deductions suffered and your bill
Your return shows your total profit, the tax and Class 4 National Insurance on it, and the CIS deductions suffered. HMRC subtracts the deductions from the bill. If they are higher than the bill, you are due a repayment. If they are lower, you pay the difference.
Remember that your Uber, Bolt or delivery profit adds to the same bill. CIS deductions only cover tax on your total income, not just the CIS work. Our self-employed driver tax checklist for CIS shows how to keep both income streams in order.
Why the payment can drop to nothing
If your deductions cover more than 80% of the tax you owed, no payments on account are requested. This often catches subcontractors out in the opposite direction too. A year with less CIS work and more self-employed driving income can leave a big July bill that nobody planned for.
How are payments on account calculated with CIS deductions?
HMRC bases each payment on account on your previous year's bill after tax already collected at source, then divides it by two. So CIS deductions reduce the starting figure. Your HMRC statement shows the amounts requested, which is the number to trust, and the worked example below shows the arithmetic.
GOV.UK describes the payment as roughly half of last year's tax. We therefore recommend checking your statement rather than doing the sums on trust, because small items such as underpaid tax through your code can change the base.
Worked example: a courier driver with CIS income
This is an illustrative example. Maya (an invented driver) delivers parcels in her own van and takes weekend subcontract work with a building contractor. Figures are rounded and for explanation only.
| Item | Amount |
|---|---|
| 2025/26 income tax and Class 4 National Insurance | £7,000 |
| CIS deductions suffered in 2025/26 | £2,600 |
| Balance not collected at source | £4,400 |
| Share collected at source (£2,600 / £7,000) | About 37%, so below 80% |
| Each payment on account (£4,400 / 2) | £2,200 |
| Due on 31 January 2027 and 31 July 2027 | £2,200 each |
Maya's CIS deductions are only about 37% of the bill, so she is not exempt. Her payments are £2,200 each, rather than £3,500 each if there had been no deductions. That £1,300 difference per payment is the benefit of CIS credit.
Now suppose in 2026/27 Maya expects her van profit to fall and her CIS deductions to rise to £4,000, with a total bill of about £6,000. The balance after CIS would be about £2,000. Her payments on account of £2,200 each would then be more than needed, so she may ask HMRC to reduce them.
Can I reduce my payments on account?
Yes. You can claim to reduce your payments on account if your business profits or other income fall, your tax relief increases or the tax deducted at source rises. As GOV.UK explains in its guidance on how to claim to reduce payments on account, you apply online or by posting form SA303.
You must give a reason and a figure of your own. HMRC does not work out the reduced amount for you. GOV.UK says you must claim by 31 January after the end of the tax year, so do not leave it until the last minute.
Good reasons to reduce
- Your CIS work has increased, so more tax is being deducted before you are paid.
- Your driving profits have fallen because you worked fewer hours, had vehicle costs or lost income.
- You have new allowable expenses or capital allowances, such as a vehicle purchase.
- You stopped one income source, such as a rental or a contract.
When not to reduce
Do not reduce just to free up cash. If your final bill turns out higher than your reduced payments imply, HMRC charges interest on the shortfall from each original due date. A penalty can apply in some cases where a reduction was careless. Keep records that support your estimate.
How do I reduce a payment on account, step by step?
To reduce a payment on account, estimate your tax bill for the current year, work out the reduced payments, then apply online through your HMRC account or with form SA303. Keep your workings with your records. Below is the process we follow with clients who have CIS income.
- Gather your year-to-date CIS payment and deduction statements from each contractor, plus your driving income and expense records.
- Estimate your profit for the whole tax year, including both CIS and self-employed driving income.
- Work out the tax and Class 4 National Insurance on that profit, using the current rates on GOV.UK. Our tax calculator gives a quick guide.
- Subtract the CIS deductions and any other tax collected at source to find the balance you will actually owe.
- Compare that balance with the payments on account HMRC has requested. If your estimate is lower, work out the new half-payment figure.
- Apply online or with form SA303, giving the reason and the new amount, and keep a copy of your workings.
- Check your HMRC statement afterwards to confirm the reduced figure appears before you pay on 31 July.
What happens if I pay late or cannot pay?
If you pay late, HMRC charges interest on the amount owed from the due date until it is paid, and may charge penalties. You should not ignore a bill you cannot afford. Contact HMRC before the deadline to ask about a payment plan, because acting early keeps the cost down.
According to HMRC's guidance on Self Assessment penalties, late payment penalties are 5% of the unpaid tax at 30 days, 6 months and 12 months, and interest is charged as well. The current interest rate changes over time, so check it on GOV.UK rather than relying on an old figure.
If paying in full is difficult, GOV.UK lists support on its difficulties paying HMRC page. You can also pay towards your bill in instalments before the deadline, using weekly or monthly payments.
How and when should I pay the 31 July bill?
Pay by midnight on 31 July, and allow time for the money to reach HMRC. The GOV.UK guide to paying your Self Assessment bill says online banking and card payments can arrive the same or next day, Bacs takes about three working days, and a new Direct Debit takes five.
Use your 11-digit Unique Taxpayer Reference (UTR) as the payment reference, and pay from your own account. For a practical walk-through of the online route, see our guide to paying Self Assessment online.
What is different if I have gross payment status?
With gross payment status, contractors pay you in full with no tax deducted, so nothing is collected at source. Your payments on account then rest on the whole bill, and the 80% exemption is unlikely to apply. You carry the whole tax cost yourself and need to set money aside as you earn.
A simple habit helps: move a fixed share of every payment into a separate savings pot. Pay the 31 January and 31 July instalments from that pot, so the dates never cause a cash-flow squeeze.
How do payments on account compare across income types?
Your income mix decides how large the 31 July payment is. The more tax is collected at source through CIS or PAYE, the smaller your payments on account tend to be. The table shows the usual pattern, but your HMRC statement always gives the exact figures.
| Your situation | Tax collected at source | Likely effect on payments on account |
|---|---|---|
| Driver only, no CIS or PAYE | None | Both payments are based on the full bill, if it was £1,000 or more |
| Driver plus CIS at 20% deduction | Partly, through CIS | Smaller payments, as CIS credit reduces the base |
| CIS only at 30% deduction (unregistered) | Heavily | May fall below the 80% test, so possibly no payments |
| Gross payment status | None | Full-size payments, so save as you earn |
| Driver plus employment on PAYE | Partly, through tax code | Payments reduced by tax already collected |
How do I keep CIS records for the July payment?
Keep every monthly CIS payment and deduction statement from your contractors, because they prove the tax you have already paid. Without them you cannot claim the credit on your return, and your payments on account stay higher than they should. Store them next to your driving income records.
Check each statement against your bank payments, and chase any missing statement early. Contractors report deductions to HMRC monthly, so your online account should broadly match your own totals. If it does not, ask the contractor to correct it before you file.
Common mistakes and the penalty each triggers
| Mistake | What can happen |
|---|---|
| Missing the 31 July payment | Interest on the unpaid amount, and late payment penalties if it stays unpaid for 30 days, 6 months and 12 months |
| Ignoring CIS deductions on your return | You overpay tax or Class 4 National Insurance, and payments on account stay too high |
| Reducing payments too far | Interest on the shortfall from each due date, plus a possible penalty if careless |
| Assuming CIS covers the driving profit too | A large balancing payment on 31 January |
| Paying by slow methods near the deadline | Money arrives late and counts as a late payment |
| Losing contractor deduction statements | Delays in claiming credit and difficulty proving the figures |
Key terms
- Payment on account: an advance instalment towards your next Self Assessment bill, due 31 January and 31 July.
- Balancing payment: the amount that settles the difference once your return for the year is final.
- CIS deductions suffered: tax a contractor takes from your payments, which counts as an advance payment of your tax and National Insurance.
- Gross payment status: a CIS status where contractors pay you without deducting tax.
- SA303: the form used to claim a reduction in payments on account.
- UTR: the Unique Taxpayer Reference HMRC gives you for Self Assessment.
How Uber Driver Accountant helps
Uber Driver Accountant is an independent accountancy practice for drivers only, and it is not linked to Uber or Bolt. We handle CIS deductions, payments on account and reduction claims for a fixed fee, from £20 a month, so you see the cost before work starts.
Our CIS returns service checks your deduction statements, files your return and tells you what to expect in January and July. You can compare plans on our pricing page. If your driving also changes your tax position, see what is new in Self Assessment for 2026/27.
Next steps before 31 July
Check your HMRC online account now, gather your CIS statements and estimate this year's bill. If your numbers look different from last year, consider a reduction claim. Contact us for a plain-English review, and compare how the rules fit with Self Assessment and Making Tax Digital.
Last reviewed 3 October 2026 by the Uber Driver Accountant tax team.
This article is general information and is not personal tax advice. Speak to a qualified accountant about your own circumstances, and use professional representation if HMRC disputes a figure or raises a penalty.
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