A subcontractor’s invoice lands on your desk, the payment is due, and you are not sure whether to deduct 20%, 30%, or nothing at all. That is exactly where a simple process makes the difference. Knowing how to organise CIS deductions means you can pay people correctly, submit returns on time and avoid the worry of discovering a problem months later.
For small construction businesses, CIS administration can feel like one more demand on an already busy week. The good news is that it becomes much more manageable when every subcontractor and every payment follows the same clear routine.
Start by knowing which payments fall under CIS
The Construction Industry Scheme applies when contractors pay subcontractors for construction work. This can include work such as building, decorating, demolition, repairs and site preparation. It is not limited to large building firms. If your business pays subcontractors for qualifying work, CIS may apply even when construction is not your main business activity.
Before making a first payment, check whether the work is covered and whether the worker is genuinely self-employed. CIS is not a substitute for employment status checks. Someone who works under your direction, uses your equipment and has little control over how or when they work may need to be on payroll instead. Getting this point right protects both your business and the individual.
It also helps to review invoices carefully. CIS deductions are normally calculated on the labour element of a payment, excluding VAT and the cost of materials. Where an invoice includes labour and materials together, ask the subcontractor to show a clear breakdown. A vague invoice creates extra work later and can lead to too much tax being deducted.
Register and verify before you pay
Once you are registered as a CIS contractor, every new subcontractor should be verified before their first payment is processed. Verification confirms the deduction rate you should use.
In most cases, the result will be one of three outcomes: gross payment, where no deduction is made; the standard 20% deduction rate; or a higher 30% rate where the subcontractor cannot be verified in the usual way. Do not rely on what a subcontractor tells you their rate should be. Keep the verification result with their records so you have a clear audit trail.
Create a straightforward subcontractor file from the outset. Whether you keep this digitally or in a paper file, it should contain their full name or business name, address, Unique Taxpayer Reference where provided, National Insurance number or company details as relevant, verification reference, bank details and copies of invoices. Keep proof of any material costs separately too.
A cloud accounting system or payroll software can make this easier, but software only works well when the information going into it is correct. A tidy spreadsheet can also work for a small number of subcontractors, provided it is updated every time a payment is made.
Build a payment routine around the tax month
The CIS tax month runs from the 6th of one month to the 5th of the next. Organising your deductions around these dates is far less stressful than trying to reconstruct payments at month end.
When an approved subcontractor invoice is ready to pay, record the gross amount, material costs, VAT, labour amount, applicable deduction rate, tax deducted and net payment. Save the invoice alongside the record. If you make payments in stages, record each one separately rather than waiting for the job to finish.
A practical routine is to update your CIS records on the same day you make each payment. That means there is no mystery about what has been paid, what has been deducted or which tax month it belongs to. It also gives you a clearer picture of the cash you are holding to pay to HMRC.
For each payment, your record should show enough detail to explain the calculation. In practice, that includes:
- the subcontractor’s name and verification status
- the date and value of the payment
- the labour, materials and VAT split
- the CIS deduction made and the net amount paid
- the invoice number and supporting documents
This is particularly helpful when a subcontractor queries their payment. You can answer promptly and calmly, rather than searching through messages and bank statements.
Submit the monthly return and pay HMRC on time
A CIS monthly return is normally due by the 19th of the month following the end of the tax month. For example, payments made between 6 April and 5 May are reported by 19 May. If you have not paid any subcontractors during a tax month, you may need to submit a nil return or tell HMRC that you are inactive, depending on your circumstances.
The deductions you have made are paid to HMRC as part of your PAYE liabilities. When paying electronically, the payment is generally due by the 22nd following the end of the tax month. Setting money aside as each deduction is made is a simple but valuable habit. It prevents the common problem of using funds that were never really available to spend.
Put two recurring reminders in your diary: one shortly after the 5th to review and reconcile your records, and another before the 19th to submit the return. Do not leave the task until the deadline day. If a payment has been allocated to the wrong month or an invoice is missing, you will have time to put it right without panic.
Late returns can lead to penalties, even where no tax is due. A regular process is therefore not just about being organised – it is a way to reduce avoidable costs and protect your reputation.
Give subcontractors clear deduction statements
Subcontractors need a monthly deduction statement showing what you have paid them and what tax has been deducted. This should be provided within 14 days of the end of the tax month.
The statement allows the subcontractor to claim credit for deductions against their own tax bill. It also gives them confidence that their records match yours. If you pay the same people regularly, issuing statements as part of your month-end routine is much easier than trying to produce them months afterwards.
Keep a copy of every statement you issue. CIS records must be retained for at least three years after the end of the tax year they relate to, so a clear digital filing system can save a great deal of time if HMRC asks questions later.
Deal with changes as they happen
Construction work is rarely perfectly predictable. A subcontractor may change their address, send an amended invoice, stop working for you or move from self-employment onto your payroll. Treat these as record-keeping events, not details to sort out when you have time.
If an error is spotted after a return has been submitted, do not ignore it. The right correction depends on what has gone wrong and when you find it. In many cases, the next monthly return can be amended, but it is sensible to check the position before making changes. Trying to fix an error by quietly changing a later payment can make your records harder to understand.
It is also worth separating CIS money from general cash flow planning. A deduction made from a subcontractor is not extra profit for the business. Recording it as a liability until it is paid to HMRC gives you a more honest view of the cash available to you.
How to organise CIS deductions when time is tight
If you are running jobs, speaking to customers and managing suppliers, the real challenge is often not understanding CIS rules but finding a process you can stick to. Keep it simple: verify once, record every payment straight away, check the month after the 5th, submit before the 19th and issue statements as part of the same routine.
For a growing business with several subcontractors, outsourced CIS payroll or bookkeeping support can take the monthly pressure away while keeping you informed. At Angel Bookkeeping & Payroll Services, the focus is on clear records and friendly, practical support, so you know what has been paid, what is due and what needs your attention.
CIS does not need to take over your evenings. A few reliable habits, supported by accurate records, can give you the confidence to pay subcontractors properly and get back to running the work that keeps your business moving.