If you work in construction as a subcontractor, CIS is likely to affect how and when you get paid. It is one of the most important tax systems in the industry, yet it is often misunderstood. Many subcontractors know that “something gets taken off” by the contractor, but are less clear on what that deduction actually means for cash flow, bookkeeping, Self Assessment, limited company payroll, or refunds.
Under the Construction Industry Scheme, contractors deduct money from subcontractor payments and pass it to HMRC. Those deductions are not a separate tax. They are advance payments towards the subcontractor’s tax and National Insurance liabilities. Contractors must register for CIS, while subcontractors do not have to register, but unregistered subcontractors are usually paid at the higher deduction rate.
CIS affects Subcontractors because it affects far more than tax admin. It affects what reaches the bank account, how expenses should be tracked, what records must be kept, and how the final tax position is worked out. HMRC also makes clear that subcontractors remain responsible for paying the correct tax overall, even where deductions have already been made throughout the year.
What CIS means for subcontractors
HMRC’s subcontractor guidance says CIS generally applies where you work for a contractor in construction as a sole trader, limited company owner, or partner in a partnership or trust. Under standard net payment status, a contractor deducts 20% from your payments and sends it to HMRC.
Before paying a new subcontractor, the contractor must verify them with HMRC. HMRC then confirms whether the subcontractor is registered and which deduction rate applies, or whether the subcontractor can be paid without deductions.
That means CIS affects you from the first payment, not just at year end. A busy month on site does not automatically mean strong cash flow, because part of the labour payment may already have been withheld before it reaches you. This is one reason why CIS can feel tougher in practice than it sounds on paper. The system is designed to prepay tax, but the trade-off is less immediate cash in hand for the subcontractor. That conclusion follows directly from HMRC’s description of CIS deductions as advance payments and from the deduction mechanism itself.
How CIS deductions work
For most subcontractors, the key rates are straightforward. HMRC says deductions are generally made at 20% for registered subcontractors, 30% for those who are unregistered, and 0% where gross payment status applies.
The deduction is not simply a final tax bill. It is a payment on account. HMRC’s guidance says subcontractors are still responsible for the correct tax and National Insurance for their business, even if deductions have been made throughout the year.
HMRC also says contractors must give subcontractors a payment and deduction statement within 14 days of the end of each tax month when deductions have been made. Those statements are essential because they show what was paid and what was deducted.
How CIS Affects Subcontractors cash flow
The most immediate impact of CIS is on cash flow. In a non-CIS trade, a self-employed person may receive the gross amount and set money aside later for tax. Under CIS, some of that money is already withheld before payment is received.
That can create pressure around:
Fuel, tools and van costs
Ongoing working costs still need to be paid, even though part of the income has been sent to HMRC first.
Materials and site expenses
Margins can feel tighter when deductions are taken from labour payments and operating costs continue as normal.
Household budgeting
For sole traders especially, lower net receipts can make personal budgeting harder during quieter periods.
This is why bookkeeping matters so much for subcontractors. HMRC says monthly statements should be used to help calculate whether you still owe tax and National Insurance or are due a refund. In practice, that means you need to track invoices, receipts, statements and expenses together, not separately.
Gross payment status explained
Gross payment status allows subcontractors to be paid without CIS deductions being taken at source. HMRC says that under this status, contractors do not deduct CIS before paying you.
This can improve cash flow because more money stays in the business during the year. But it does not remove tax responsibility. The subcontractor still needs to file correctly and pay liabilities through the normal process.
HMRC and HM Treasury guidance on CIS reform from 6 April 2024 says VAT compliance was added to the statutory compliance test for being granted, and for keeping, gross payment status.
So gross payment status can be valuable, but it suits subcontractors who already have strong financial controls. Better cash flow is useful only when the business is organised enough to manage the later tax bill properly.
Why record keeping is essential
CIS works properly only when records are complete. HMRC says contractors give monthly statements of payments and deductions, and those statements help subcontractors with accounting and tax calculations.
A strong CIS record-keeping system should include:
Invoices raised
You need a full record of what you charged and when.
Payment and deduction statements
These are the evidence of CIS deducted at source. HMRC says they must be issued within 14 days of the end of each tax month where deductions are made.
Expense records
These support the final profit calculation and help determine whether the CIS deducted was too much, too little or broadly correct.
Bank records
These help reconcile what was invoiced against what was actually received.
When records are poor, subcontractors often struggle to prove deductions suffered, spot errors early, or claim refunds quickly. That is one reason bookkeeping support can save time and money later.
CIS and year-end tax
CIS does not replace year-end reporting. HMRC says you are still responsible for paying the correct tax and National Insurance even if deductions have been made all year.
For sole traders, that usually means claiming CIS deductions through Self Assessment. For limited companies, HMRC says CIS deductions suffered should be reclaimed through the company’s monthly payroll scheme, not through the Corporation Tax return.
That distinction is important. Many subcontractors assume CIS automatically settles everything, but the final tax position still depends on profit, expenses, and business structure. Some people owe more at year end. Others have overpaid and are due money back.
CIS refunds
A CIS refund usually happens where the deductions made during the year are more than the final amount due. HMRC provides different routes depending on the business type.
For individuals, HMRC provides an in-year repayment process through form CIS40. For limited companies, HMRC says CIS deductions should first be offset against monthly PAYE liabilities, with a separate company refund route available in some cases. HMRC’s company refund guidance says current-year claims may need supporting evidence such as payment and deduction statements and bank statements.
In practice, delayed refunds are often caused by incomplete records, missing statements, or claims being made through the wrong route.
Common CIS mistakes subcontractors should avoid
A few mistakes come up repeatedly.
Not registering early
Subcontractors do not have to register, but HMRC says deductions are taken at a higher rate if they are not registered.
Assuming CIS settles the whole tax bill
HMRC says you still have to pay the correct tax and National Insurance overall.
Losing deduction statements
Without them, it is harder to reconcile payments and support refund or year-end claims.
Ignoring employment status
HMRC says contractors must check whether someone should be employed instead of subcontracted.
Weak bookkeeping
Poor records make CIS harder to manage and often lead to missed credits or delayed refunds.
How LT Accounting can help
CIS works best when the numbers are kept under control throughout the year, not just when deadlines arrive. LT Accounting can help subcontractors with bookkeeping, Self Assessment, payroll, management accounts, year-end accounts, VAT returns and wider CIS support.
That means helping you:
Keep accurate bookkeeping
So invoices, expenses and CIS statements all match up.
Stay on top of Self Assessment or payroll claims
So CIS deductions are reported in the right place.
Improve cash flow visibility
So you know what has been invoiced, what has been received, and what may still be due to HMRC.
Handle refunds and compliance properly
So overpayments are not left unresolved longer than necessary.
For subcontractors, good accounting support is not just about compliance. It helps reduce stress, improve visibility and protect working capital.
Need Help?
Need help with CIS, bookkeeping, Self Assessment, payroll, VAT returns or year-end accounts? LT Accounting supports UK subcontractors with practical accounting support that keeps records accurate, deductions properly tracked and tax obligations under control.
FAQ
Does CIS mean I do not need to file a tax return?
No. HMRC says CIS deductions are advance payments, and subcontractors are still responsible for paying the correct tax and National Insurance overall.
What CIS rate applies to subcontractors?
HMRC says the usual rates are 20% for registered subcontractors, 30% for unregistered subcontractors, and 0% for those with gross payment status.
Do contractors have to give CIS statements?
Yes. HMRC says contractors must give a payment and deduction statement within 14 days of the end of each tax month where deductions were made.
Can a subcontractor get a CIS refund?
Yes. HMRC provides repayment routes for overpaid CIS, including form CIS40 for individuals in the current tax year and a separate route for limited companies in some cases.
Does gross payment status remove tax responsibilities?
No. It means contractors do not deduct CIS at source, but the subcontractor still has to meet their tax obligations through the normal process.
