Blog / Construction Software
BuildersAI Team 8 min read Quick Answer
CIS compliance software automates Construction Industry Scheme requirements by verifying subcontractors with HMRC, calculating deductions at the correct rate (0%, 20%, or 30%), generating monthly CIS300 returns, and maintaining audit trails. With April 2026 changes making nil returns mandatory and increasing liability for incorrect deductions, the right software prevents costly HMRC penalties while saving 5-10 hours per month on manual paperwork.
If you’re a UK contractor working with subcontractors, CIS isn’t optional. Get it wrong and you’ll face penalties and HMRC investigations. Get it right and compliance becomes a background task.
This guide covers how CIS software works, April 2026 changes, and which platforms deliver. Whether you’re on spreadsheets or evaluating your current system, you’ll know what good CIS software looks like.
The Construction Industry Scheme (CIS) is HMRC’s tax collection system for the construction industry. Unlike standard employment where you deduct PAYE and National Insurance, CIS requires contractors to deduct tax from subcontractor payments and report those deductions monthly.
Here’s how it works in practice:
When you pay a subcontractor £1,000, you don’t simply transfer £1,000. First, you verify them with HMRC to determine their deduction rate. If they’re registered for gross payment (0% deduction), they receive the full amount. If they’re registered at the standard rate, you deduct 20% (£200) and pay them £800. If they’re not registered at all, you deduct 30% (£300) and pay them £700.
You then report these deductions to HMRC through a monthly CIS300 return, due by the 19th of the following month. HMRC credits these deductions against the subcontractor’s tax bill, similar to how PAYE credits work for employees.
Why this matters:
For official CIS requirements, see HMRC’s Construction Industry Scheme guidance and the GOV.UK CIS overview.
For contractors making regular subcontractor payments, CIS compliance represents a significant administrative burden. Software doesn’t eliminate the responsibility, but it does eliminate most of the manual work.
CIS operates on three deduction rates, determined by the subcontractor’s registration status with HMRC:
Who qualifies: Subcontractors who have passed HMRC’s compliance and turnover tests. Requirements include:
What it means: No deductions are made from payments. The subcontractor receives the full invoice amount and handles their own tax payments.
Contractor responsibility: You must still verify gross payment status before each payment and include these payments in your CIS300 return with a zero deduction amount.
Who qualifies: Subcontractors registered with HMRC for CIS but not approved for gross payment status. This includes:
What it means: You deduct 20% from the labour portion of their invoice (materials are excluded from CIS deductions) and pay the remainder.
Example: Invoice for £2,000 (£1,500 labour + £500 materials)
Who qualifies: Subcontractors who haven’t registered with HMRC for CIS. This is the default rate for unverified subcontractors.
What it means: You deduct 30% from the labour portion, regardless of their circumstances.
Example: Same £2,000 invoice (£1,500 labour + £500 materials)
Critical point: You must use the 30% rate if HMRC verification fails or if you don’t verify at all. “I didn’t know” is not an acceptable defence, particularly with the April 2026 CIS changes introducing stricter liability rules.
CIS deductions only apply to the labour element of an invoice. Materials purchased by the subcontractor and included in their invoice are exempt from deductions.
The complication: Invoices must clearly separate materials from labour. If they don’t, HMRC’s position is that the entire amount is labour and subject to deduction. Good CIS software forces this separation at the invoice entry stage, preventing accidental over-deductions.
Verification is mandatory before making the first payment to a subcontractor in each tax year (or before their first payment if they’re new). This process checks their CIS registration status and determines the correct deduction rate.
Without software, verification requires:
Time cost: 5-10 minutes per subcontractor, multiplied by dozens or hundreds of subcontractors each year.
CIS-compliant software handles this automatically:
Time cost: 30 seconds for initial entry, then fully automatic.
April 2026 CIS changes: The new “knew or should have known” standard means you must maintain current verification records. If a subcontractor’s status changes and you continue using an outdated rate, you’re liable for the shortfall plus penalties , even if they didn’t inform you of the change. This makes regular reverification essential, not optional.
If verification fails, you have two options:
You cannot make payments to unverified subcontractors at 0% or 20%. Doing so puts you on the hook for the full deduction amount, plus penalties.
The CIS300 return is your monthly report to HMRC, listing all payments made to subcontractors and the deductions taken. It’s due by the 19th of the month following the tax month (which runs from the 6th to the 5th, not calendar months).
For each subcontractor you paid during the tax month, you must report:
If you made no payments to subcontractors, you must now file a nil return following the April 2026 CIS changes (previously, you could skip months with no activity). This affects all contractors, including those with seasonal or irregular subcontractor usage.
Tax months run from the 6th to the 5th (e.g., 6 April - 5 May), with returns due by the 19th of the following month. If the 19th falls on a weekend or bank holiday, the return is due on the last working day before.
Manual process:
Time cost: 2-4 hours for contractors with 10-20 subcontractors; significantly more for larger operations.
Software-automated process:
Time cost: 10-15 minutes for review and submission, regardless of subcontractor count.
CIS deductions must be paid to HMRC by the 19th of the month following the tax month (same deadline as the CIS300). Payment methods include:
Good CIS software displays your total liability and payment deadline on the dashboard, ensuring you never miss a payment.
Two significant changes increased compliance requirements:
Previously, you could skip months with no subcontractor payments. The April 2026 CIS changes now require you to file a nil return every month , 12 returns per year regardless of activity. Missing a nil return triggers the same penalties as missing a standard return (starting at £100).
HMRC can now hold you liable for deduction shortfalls if you “knew or should have known” the rate was incorrect , even if the subcontractor provided wrong details.
What this means:
Example: A subcontractor claims gross payment status. You don’t verify and pay at 0%. HMRC later determines they were never approved. Under the April 2026 CIS changes, you’re liable for the full shortfall plus penalties , even though they misled you , because you “should have known” to verify.
Bottom line: Following the April 2026 CIS changes, software with automatic reverification and audit trails is now essential, not optional.
The VAT Domestic Reverse Charge (DRC) can apply alongside CIS on the same transaction. Under DRC, you (the customer) account for VAT instead of the subcontractor. CIS deductions still apply to the labour portion only.
Key points:
Good CIS software flags reverse charge invoices and handles both schemes correctly. For details on accounting integration, see Construction Software Accounting Integration UK.
Must-have features:
Red flags to avoid:
Most construction software doesn’t include robust CIS functionality. Here are the platforms that do:
Sage 300 CIS (5/5) , The gold standard. Full HMRC integration, automatic reverification, comprehensive audit trails. Best for contractors with dedicated finance teams. Expensive (£50-100+/month) and desktop-focused.
Archdesk (4/5) , Good HMRC integration and accounting software sync. Reverification is manual and audit trails are basic, but solid for mid-sized contractors needing CIS within broader project management.
Procore & ToolTime (2/5) , Basic payment tracking only. No HMRC integration, manual verification and returns required. CIS is an afterthought.
Fieldwire, PlanGrid, Buildertrend (0/5) , No CIS functionality. These are site coordination or US-focused tools.
BuildersAI (0/5 for CIS) , Currently focused on mobile site management, AI document search, and offline project coordination. No CIS features yet , pair with Sage or Archdesk for compliance.
| Platform | HMRC Integration | Auto-Verify | CIS300 Submit | Best For |
|---|---|---|---|---|
| Sage 300 CIS | Yes | Yes | Yes | Full compliance |
| Archdesk | Yes | Manual | Yes | Mid-sized contractors |
| Procore/ToolTime | No | No | No | Separate CIS handling |
For pricing details, see Construction Software Pricing UK.
Even with software, CIS compliance can go wrong. Here are the costly mistakes to avoid:
| Mistake | Penalty | Prevention |
|---|---|---|
| Late CIS300 returns | £100 (1 day late), escalating to £300+ or 5% of deductions | Automatic reminders and one-click submission |
| Wrong deduction rate | Full shortfall owed + interest + up to 100% penalty for deliberate errors | Automatic verification at payment time |
| Failure to verify | You owe HMRC 30% even if you paid subcontractor gross , unrecoverable | Require verification before payment entry |
| Materials not separated | Over-deduction disputes, amended returns required | Force materials/labour split at invoice entry |
| Late HMRC payment | Daily interest + penalty charges for repeat offenders | Set up Direct Debit |
| Missing nil returns (April 2026 CIS changes) | Same as late returns , £100+ | Software prompts for inactive months |
| Poor record-keeping | Estimated assessments during audits (up to 6 years back) | Immutable digital audit trails |
The cost of a single verification failure can run into thousands. Software that prevents these mistakes pays for itself many times over.
Yes. Even with 2-3 subcontractors, manual verification and returns take hours monthly. More importantly, a single verification failure can cost thousands in penalties , far more than software costs. If you make any subcontractor payments, CIS software pays for itself.
Xero and QuickBooks handle basic CIS (verification and returns), but lack job costing, site documentation, and mobile access. For office-only businesses, they may suffice. For site-based teams, construction software with accounting sync is more efficient.
Always use the HMRC-verified rate, not what the subcontractor claims. Inform them of the discrepancy so they can contact HMRC. Under the April 2026 rules, you’re liable for using incorrect rates even if the subcontractor misinformed you.
Minimum three years, but HMRC can investigate up to six years back (20 years for fraud). Best practice: keep records for six years. Good software stores them indefinitely.
Yes. Company structure doesn’t exempt them. Verify using their UTR and apply the rate HMRC confirms. The misconception that limited companies are exempt causes significant compliance issues.
No. You must reimburse the subcontractor directly and file an amended CIS300. This is why automatic verification and materials/labour separation matter.
The April 2026 CIS changes made manual CIS compliance both slower (mandatory nil returns) and riskier (increased liability). The right software protects you from penalties that can run into thousands for a single mistake.
Look for full HMRC integration, automatic verification, and comprehensive audit trails. The difference between basic and proper CIS functionality often costs less than £20/month but can save thousands in penalties.
For broader UK construction software features, see our construction software comparison or the construction project management software guide.
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BuildersAI Team
Construction Technology Experts
The BuildersAI team combines decades of UK construction industry experience with technology expertise. Our writers include former site managers, quantity surveyors, and construction consultants who understand the daily challenges of running building projects.
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