CIS accounting

CIS, GPS and employer NIC compliance for multi-trade building firms.

Multi-trade building firms carry more moving parts than almost any other construction business. A single project may involve bricklayers, plasterers, joiners, roofers, plumbers and electricians, each a separate CIS subcontractor with their own verification status, deduction rate and monthly return entry. At company level, the GPS anti-fraud rules from April 2026 mean the volume of subcontractor payments is now also a volume of due-diligence events. At the same time, the employer NIC increase to 15% from April 2025 has changed the economics of directly employing versus subcontracting for each trade. Directors and finance teams need a system, not a spreadsheet.

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19th

Monthly CIS300 deadline: penalties start the day after

15%

Employer NIC from April 2025, threshold £5,000 pa

£100,000

GPS total turnover threshold for a multi-director building company

The specific challenges

What makes multi-trade building firms accounting different.

High-volume subcontractor verification and the April 2026 due-diligence duty

Finance Act 2026 (Royal Assent 18 March 2026) requires a contractor to re-verify each subcontractor's CIS status before every payment, run a Companies House legitimacy check, and carry out bank account name verification as part of the should-have-known due-diligence standard. For a multi-trade firm running five to ten trades on a single project and paying weekly or fortnightly, that is a significant process obligation. Failure to carry out and document the checks is, in itself, sufficient for HMRC to revoke GPS under the immediate-revocation power introduced by the same Act.

CIS300 returns: deadline, nil months and penalty ladder

The CIS300 monthly return must be filed by the 19th of the following tax month. From 6 April 2026, a nil return is required in any month where the firm makes no subcontractor payments. Multi-trade firms working on long projects with phased payment schedules often have months where subcontractor payments fall in an awkward pattern: a nil return in the wrong month, or a payment misattributed to the wrong tax month, creates a penalty exposure starting at £100 per late return and escalating at two, six and twelve months.

Employer NIC at 15% on directly employed site staff

For multi-trade firms that employ site managers, labourers and plant operators directly alongside CIS subcontractors, the April 2025 increase in employer NIC to 15% above £5,000 raises the employment cost per head relative to prior years. The interaction with auto-enrolment (minimum 3% employer pension contribution) and any SSP or contractual sick pay obligations makes the total employment cost per directly employed worker higher than it has been since the 2019 reform. We model the comparative cost of direct employment versus CIS for each trade category.

GPS at company level and the turnover test under multi-director structures

For a limited company with multiple directors, GPS requires net annual CIS turnover of £30,000 per director or £100,000 total. On large-scale multi-trade building projects with significant materials procurement (aggregates, bricks, timber, steel, plasterboard), the materials strip-out from the turnover calculation matters. Net CIS turnover excludes VAT and the cost of materials purchased for jobs. Firms frequently understate their qualifying turnover because they start from total invoiced revenue rather than the labour-only net CIS figure.

How we help

What we do for multi-trade building firms.

CIS300 return management and nil-return compliance

We prepare and file your CIS300 monthly return on time, verify each subcontractor's status before each payment run, issue compliant payment and deduction statements within 14 days, and handle nil returns for inactive months from April 2026. For firms with a large, fluctuating subcontractor pool across multiple trades, we maintain the verification record that protects you under the April 2026 due-diligence rules.

GPS application and anti-fraud due-diligence workflow

We calculate your net CIS turnover by trade and project, apply the correct per-director threshold for your company structure, and manage the GPS application and three qualifying tests. From April 2026, we implement the pre-payment due-diligence workflow (HMRC re-verification, Companies House check, bank account name verification) and maintain the documentation trail that meets the should-have-known standard under Finance Act 2026.

Employer NIC planning across your workforce mix

We model the total employment cost of your current workforce by category: directly employed, CIS subcontractor, and limited-company contractor. The April 2025 NIC regime changes the relative cost at the margins and the calculation differs by trade, income level and project type. We advise on structuring decisions at the point where they make a genuine difference, not in retrospect.

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“We were filing the CIS300 but the nil-return obligation had come back in April and nobody had told us. We had three missing returns before we picked it up. Getting a firm to manage the full monthly process took that risk off the table.”

Director, multi-trade building contractor, Midlands

Composite snapshot based on client patterns. Name and figures anonymised. The tax mechanics are real.

Questions from multi-trade building firms

We have eight directors. What is our GPS turnover threshold?

The test for a limited company requires net annual CIS turnover of £30,000 per director or £100,000 total, whichever threshold is relevant to your structure. Eight directors at £30,000 each would be £240,000, but the £100,000 total cap means the effective threshold is £100,000 net of materials and VAT. Net CIS turnover excludes the cost of materials purchased for jobs and VAT. We calculate your qualifying figure precisely from your labour income across all projects.

We pay subcontractors from multiple trades every week. Do we need to re-verify them before every payment under the April 2026 rules?

Under Finance Act 2026, the should-have-known standard requires that a contractor take reasonable steps to verify the legitimacy of each subcontractor before each payment. HMRC's due-diligence guidance identifies three steps: CIS verification with HMRC, a Companies House check, and bank account name verification. For a high-frequency, multi-trade payment run, we build this into your payroll and payments process as a systematic pre-payment check rather than a manual one-off, so the records exist for every subcontractor payment without creating an operational bottleneck.

We had no subcontractor payments in two months this year. Do we still need to file CIS300 returns for those months?

Yes, from 6 April 2026. The nil-return obligation was reinstated for all registered CIS contractors. For any tax month in which you make no subcontractor payments, you must file a CIS300 nil return by the 19th of the following month, or pre-notify HMRC of inactivity. A late or missing nil return carries a penalty starting at £100, escalating at two, six and twelve months. We manage this as part of the monthly return process so inactive months are never missed.

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Book a free call. We will talk through your CIS position, your deduction history and whether there is anything worth changing. No hard sell, no obligation.

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Specialist in CIS and construction accounting, not a generalist practice

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24-hour response guarantee

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Fixed fees, quoted before we start

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Other trades we work with

Plumbers Electricians Joiners and Carpenters Groundworkers Roofers

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