Construction bookkeeping must account for subcontractor payments, Construction Industry Scheme deductions, materials, plant hire, payroll, VAT and income earned across different projects. A building or trades business can appear busy and profitable while still facing cash-flow pressure because tax deductions, supplier invoices and project costs have not been recorded correctly.
The bookkeeping process should distinguish contractors from subcontractors and show both the gross value of work and the deductions affecting payment. Recording only the amount received or paid through the bank can understate turnover, conceal costs and leave CIS balances unexplained.
Construction businesses also need to separate routine expenses from equipment purchases, project costs and private expenditure. The accounting structure should reflect how the business works rather than forcing every transaction into broad categories that provide little useful information.
Why construction bookkeeping requires a specific process
A construction business may operate as a contractor on one project and a subcontractor on another. It may pay subcontractors under CIS while also suffering deductions from payments received from larger contractors.
Materials may be purchased for individual jobs, plant may be hired temporarily and labour costs may be spread across employees and subcontractors. Customer invoices may also be raised in stages, with retention amounts withheld until work has been completed or defects have been addressed.
These transactions need to be recorded according to what they represent. Combining subcontractor labour, materials, equipment and payroll into one cost category makes it difficult to assess project margins or confirm that CIS has been handled correctly.
Regular processing is particularly important because CIS returns operate monthly. Leaving the bookkeeping until the VAT quarter or year end can mean that filing information is already overdue by the time the records are reviewed.
When a construction business becomes a CIS contractor
A business operating within construction is generally a mainstream CIS contractor when it pays subcontractors for construction work. This can include builders, property developers, labour agencies and other businesses undertaking qualifying construction operations.
A business whose main activity is outside construction can also become a deemed contractor. The current test applies where it spends more than £3 million on construction work during a rolling 12-month period.
HMRC’s guidance on who is covered by the Construction Industry Scheme explains the distinction between mainstream and deemed contractors and the types of work covered.
A business should not wait until the threshold has already been exceeded before reviewing its position. Organisations with substantial premises, refurbishment or development programmes may need to monitor construction expenditure throughout the year.
Registration and classification under CIS are tax matters. Where the business is uncertain whether a contract or activity falls within the scheme, advice should be obtained from an appropriately qualified tax professional.
Verifying subcontractors before payment
A CIS contractor must normally verify a subcontractor with HMRC before making the first payment. The verification result tells the contractor whether to pay the subcontractor gross or deduct CIS at the standard or higher rate.
The standard deduction rate is 20 per cent. A higher rate of 30 per cent generally applies where the subcontractor is not registered, cannot be verified or has supplied details that do not match HMRC’s records. Subcontractors with gross payment status can be paid without a CIS deduction.
The contractor should retain the verification details and use the legal or trading name supplied consistently. Differences in names, business structures or Unique Taxpayer References can prevent a successful match.
Verification is not the same as deciding employment status. Before treating someone as a subcontractor, the business must consider whether the real working arrangement indicates employment. A person does not become self-employed merely because they submit an invoice or have a CIS registration.
Calculating CIS deductions correctly
CIS is not normally deducted from the complete invoice total. The contractor must first identify amounts that are excluded from the deduction calculation, such as VAT and qualifying materials paid for directly by the subcontractor.
Other exclusions can include certain plant hire, consumable stores and manufacturing or prefabrication costs, subject to HMRC’s rules and the evidence available. The CIS percentage is then applied to the remaining amount.
A subcontractor invoice should therefore separate labour, materials, VAT and other relevant charges. A single invoice description such as building work may not provide enough information for the contractor to calculate the deduction correctly.
HMRC’s guidance on making CIS deductions and paying subcontractors explains the amounts that should be removed before applying the deduction percentage.
The bookkeeping should record the gross cost of the subcontractor’s work, the CIS deducted and the net payment. Posting only the amount paid through the bank understates the subcontractor cost and fails to record the liability due to HMRC.
CIS monthly returns and payment deadlines
The CIS tax month runs from the sixth day of one month to the fifth day of the next. Contractors must report payments made to subcontractors during that period through a monthly CIS return.
The return must reach HMRC by the nineteenth day of the month following the end of the tax month. It includes subcontractors paid gross, those paid after the standard deduction and those subject to the higher deduction.
From 6 April 2026, mainstream contractors that make no subcontractor payments during a tax month must file a nil return or notify HMRC of a period of inactivity. The temporary inactivity period can cover up to six months.
CIS deductions are normally payable to HMRC by the nineteenth of the month when paid by post or the twenty-second when paid electronically, subject to weekends and bank holidays. Smaller employers and contractors meeting HMRC’s conditions may be able to pay quarterly, although returns must still be submitted monthly.
HMRC’s current CIS monthly return guidance sets out the filing process, deadlines and late-return penalties.
Providing subcontractor payment statements
Where a CIS deduction is made, the contractor must give the subcontractor a payment and deduction statement. It should show the gross payment, the amounts excluded from the deduction calculation, the CIS deduction and the resulting net payment.
The statement must generally be supplied within 14 days of the end of the relevant tax month. For a tax month ending on 5 June, it should normally be provided by 19 June.
The bookkeeping records should agree with the statement, CIS return and bank payment. Differences between these three sources should be investigated before the return is submitted.
Statements should be stored in a way that allows them to be retrieved by subcontractor and tax month. A subcontractor may need them to support a Self Assessment return, company claim or request for repayment.
Recording CIS deductions suffered by subcontractors
A subcontractor paid under deduction should record the full value of the work rather than treating the net bank receipt as total income.
If a contractor accepts a gross invoice of £5,000, deducts £1,000 under CIS and pays £4,000, the subcontractor’s records should show £5,000 of income, £1,000 deducted and the £4,000 received.
The deduction is an advance payment towards the subcontractor’s tax position rather than an ordinary business expense. How it is recovered or offset depends on whether the subcontractor operates as a sole trader, partnership or limited company.
Monthly deduction statements should be matched against invoices and bank deposits. Missing statements should be requested from the contractor rather than relying on an estimated annual total.
HMRC explains the deduction rates and statements in its guidance on how CIS subcontractors are paid.
VAT domestic reverse charge for construction services
The VAT domestic reverse charge applies to many standard-rated and reduced-rated building and construction services supplied between UK VAT-registered businesses where the services fall within CIS.
Where the reverse charge applies, the supplier does not collect the VAT in the ordinary way. The customer accounts for the output VAT and, subject to the usual recovery rules, may also claim the corresponding input VAT.
The reverse charge does not apply to every construction transaction. Exceptions can include supplies to an end user, certain intermediary suppliers, supplies outside CIS and services that are zero-rated for VAT.
The supplier should establish the customer’s VAT status, CIS status and whether the customer is an end user before issuing the invoice. The invoice should contain the appropriate reverse-charge wording and show the VAT treatment clearly.
HMRC’s guidance on the VAT domestic reverse charge for construction services explains when it must and must not be applied.
Reconciling CIS and reverse-charge VAT
CIS and the VAT reverse charge affect different parts of the transaction. CIS deductions are calculated according to the scheme’s payment rules, while reverse-charge VAT determines who accounts for VAT.
The accounting system should record the gross purchase or sale, excluded materials, CIS deduction, reverse-charge VAT and net cash movement according to the actual invoice and payment.
Automated software settings can help, but an incorrect CIS or VAT code may repeat the same error across numerous transactions. The invoice should be reviewed before it is processed rather than relying on the bank feed to determine the treatment.
VAT control accounts should be reconciled before the return is submitted. Where corrections are required, our guide to VAT adjustments in Xero explains why changes should remain supported and visible within the records.
Complex CIS and reverse-charge questions should be referred to an appropriately qualified tax adviser. The bookkeeper’s role is to apply the confirmed treatment consistently and maintain the evidence supporting it.
Materials, plant hire and subcontractor invoices
Construction businesses often purchase substantial quantities of materials or reimburse subcontractors for materials acquired for a particular project. Supplier invoices and subcontractor evidence should be retained so the costs can be verified.
A CIS contractor can ask a subcontractor for evidence that materials were paid for directly. Without suitable evidence, the contractor may need to estimate the allowable materials element when calculating the deduction.
Plant costs also need careful classification. Equipment owned by the business, plant hired from a supplier and plant supplied by a subcontractor may each need different bookkeeping treatment.
A hire-purchase or finance payment should not automatically be posted as plant hire. It may include repayment of capital, interest and charges and may relate to an asset owned by the business.
Keeping these costs separate provides clearer project reporting and gives the accountant the information needed to consider capital allowances and finance costs.
Tracking costs and income by construction project
A construction business can be profitable overall while losing money on individual jobs. Project-based reporting helps the owner compare income, materials, subcontractor labour, employee costs, plant and other direct expenses.
Customer invoices, supplier bills and subcontractor costs should be allocated to the correct project using tracking categories, projects, classes or another consistent system.
Costs shared between several jobs may need to be allocated on a reasonable basis. The method should reflect how the resource was used rather than applying an arbitrary percentage at year end.
Detailed project tracking is useful only when transactions are entered promptly and consistently. An elaborate reporting structure that is rarely maintained can produce less dependable information than a simpler system used correctly.
Businesses moving onto cloud accounting can review our guide to setting up a Xero account. The chart of accounts and tracking structure should be designed around the contractor’s projects, CIS and reporting requirements from the beginning.
Applications for payment, retentions and staged billing
Construction income may be invoiced through applications for payment, valuations, staged invoices and final accounts. The amount applied for is not always the amount certified or paid.
The bookkeeping should distinguish applications, approved invoices, disputed amounts, retentions and cash received. Recording the original application as an ordinary invoice without considering what was certified can overstate debtors and income.
Retention amounts should remain identifiable by customer and project. They may not become payable until a contractual stage is reached or the defects period has ended.
Aged receivables should therefore be reviewed alongside project and contract information. An old balance may represent a genuine overdue debt, an agreed retention or an application that was never fully approved.
Payroll and employment status in construction
A construction business may use employees, agency workers, labour-only subcontractors and specialist subcontracting companies. Each arrangement needs to be recorded according to its real nature.
CIS does not apply to payments made under a contract of employment. Putting a worker through CIS does not by itself establish that the person is self-employed.
The contractor must consider employment status and make a declaration on the CIS return. Incorrect classification can result in PAYE, National Insurance, interest and penalties becoming payable.
Payroll records should show gross wages, deductions, pension amounts, net pay and liabilities due to HMRC. These should reconcile with the accounting records and bank payments.
Businesses using cloud payroll can review our guide to setting up payroll in Xero. Software configuration should follow the confirmed employment treatment rather than deciding it.
Construction equipment and capital purchases
Vans, excavators, tools, scaffolding and other substantial equipment should be separated from routine consumables and repair costs.
The bookkeeping should retain the purchase invoice, asset description, date, VAT treatment and finance documentation. Part-exchange transactions need to show both the disposal of the former asset and acquisition of the replacement.
Capital allowances may provide tax relief for qualifying plant and machinery, but the treatment depends on the asset, ownership and use. Private use may also require an adjustment.
The bookkeeper should maintain an organised asset record without making unsupported tax claims. The accountant or tax adviser can then consider the appropriate allowances when preparing the return.
Preparing construction records for Corporation Tax
A limited construction company must maintain records sufficient to prepare its annual accounts and Corporation Tax return. Current bookkeeping helps identify income, direct costs, payroll, CIS, VAT and outstanding liabilities before the year-end process begins.
Corporation Tax is normally payable nine months and one day after the end of the accounting period for companies that are not required to pay by instalments. The Company Tax Return normally has a separate filing deadline.
Our guide to Corporation Tax deadlines and penalties explains why a company should distinguish the payment date from the filing date and maintain the records needed for both.
Year-end adjustments may still be required for depreciation, tax, work in progress and other accounting matters. Regular bookkeeping does not replace the accountant, but it provides a more dependable starting point for the annual accounts.
Good bookkeeping habits for trades businesses
Invoices and receipts should be collected as the work progresses rather than after the project has finished. Subcontractor verification details, deduction statements and CIS returns should be stored by tax month.
Bank accounts, credit cards and merchant accounts should be reconciled regularly. Unexplained payments should be investigated while the project and supplier remain familiar.
Our guide to good bookkeeping habits explains how regular document collection and reconciliation reduce the need for disruptive catch-up work.
The beginning of a new tax year is also a useful point to review subcontractor details, payroll settings, CIS registrations and outstanding balances. Our new tax year bookkeeping checklist covers the wider records and processes worth reviewing.
When outsourced construction bookkeeping helps
A sole trader with a modest number of transactions may be able to maintain the records personally. Outsourcing becomes more useful when the business begins paying subcontractors, operates as both contractor and subcontractor or needs regular project reporting.
The scope should identify responsibility for subcontractor verification, CIS calculations, returns, deduction statements, VAT processing and monthly reconciliation. It should not rely on a general promise to handle the books.
New trades businesses that need to establish their records properly can also review our guide to bookkeeping for startups. Beginning with suitable account categories and document routines is usually easier than rebuilding the file after the first year.
Bookkeeping Packages Ltd provides bookkeeping services for UK businesses, including regular processing and reconciliation according to the agreed scope.
Where responsibility for the ongoing monthly workflow needs to be transferred, our outsourced bookkeeping service explains how support can be structured.
To discuss CIS, VAT, subcontractor records and project reporting for your construction business, use the Bookkeeping Packages enquiry form.
About the Author
Stuart Kerr is Managing Director of Bookkeeping Packages Ltd, an outsourced bookkeeping service supporting UK small businesses and accountancy practices. With over 20 years of bookkeeping experience, Stuart specialises in helping businesses maintain reliable financial records and useful management information.
This article is provided for general information only. Stuart Kerr is a professional bookkeeper, not a tax, legal or regulated financial adviser. Nothing in this article constitutes tax, legal or financial advice. Advice specific to your circumstances should be obtained from an appropriately qualified professional.