The construction industry scheme is one of the HMRC most heavily enforced tax regimes. One missed monthly return, one unverified subcontractors or one wrong deduction rate and penalties start at £100 and escalate fast. There are no reminders in the post, no friendly phone calls, just automatic fines that compound while you are busy on site.
At Accountactical, we are the CIS Tax Accountant London contractors and subcontractors trust to stay compliant and maximise refunds. Whether you are a contractor filing monthly CIS300 returns or a subcontractor reclaiming overpaid tax, our CIS Accountants London team handles it all.
CIS returns are due by the 19th of every month. HMRC does not send reminders. Penalties begin at £100 for being just one day late, and they do not stop there.
The penalty structure bites harder the longer you leave it. £100 fixed penalty for one day late. £200 after two months. £300 or 5% of the CIS deductions due at six months. Tax-geared penalties up to 100% of the amount due at twelve months. The amount of this penalty will depend on why your return was late, the amount they will charge will be either £300 or 5% of any liability to make payments, or a ‘higher’ penalty of:
From April 2026, director-level personal liability of up to 30% of lost tax applies for fraud-connected transactions. This is not limited to proven fraud. HMRC can pursue directors where they believe the contractor “knew or should have known” about fraudulent activity in their supply chain. Personal assets become exposed.
Subcontractors suffer silently, as many overpay tax by thousands each year because expenses were never claimed, refunds were simply never pursued or deductions were incorrect. The money sits with HMRC while the subcontractors struggle to cover materials for the next job.
A specialist Construction Industry Scheme Accountant London based is no longer optional. It is essential for anyone who values their business, their cash flow, and their personal financial security.
CIS obligations apply more broadly than many businesses realise. Understanding where you fit in the scheme determines your compliance requirements and your risk exposure.
Contractors who pay subcontractors for construction work face mandatory CIS registration, monthly CIS300 returns, verification obligations before first payment, and correct deduction responsibilities. This includes traditional builders, property developers, renovation specialists, and any business engaging subcontractors for construction operations. The definition of construction work under CIS is broad, covering preparation, assembly, installation, finishing, and repair work. If you pay a subcontractor to do any of this, CIS likely applies.
Deemed contractors are businesses spending over £3 million annually on construction, with some guidance suggesting this threshold reduces to £1 million in certain scenarios. These businesses must register even if construction is not their main trade. Housing associations, local authorities, large property investors, and even some manufacturers who engage construction subcontractors for facility upgrades often fall into this category unexpectedly. The deemed contractor rules catch businesses that never considered themselves part of the construction industry.
Our Construction Industry Scheme Accountants London professionals facilitate every role in the supply chain. From single trade subcontractors to multi project main contractors, from deemed contractors, discovering their obligations to dual status firms navigating both sides. We make sure your CIS position is correct, optimized and compliant for your specific circumstances.
Stop risking penalties and start reclaiming your overpaid tax. Our CIS Tax Accountant London and CIS Accountants London teams deliver the compliance, refunds, and peace of mind your construction business demands.
April 2026 brought fundamental changes that every contractor and subcontractor must understand. Ignorance is no defence. HMRC expects full compliance from day one:
From 6 April 2026, contractors with no subcontractor payments in a month must file a nil return or notify HMRC in advance that no return is due. The previous exemption, which allowed contractors to simply skip months with no payments, has ended. Many contractors are unaware of this change and face unexpected penalties for months they assumed required no action. Our CIS Tax Services London include proactive nil return filing to eliminate this risk entirely.
The status of Gross payment can now be cancelled for fraud connected transactions with five year reapplication prohibition. This is not limited to proven fraud. HMRC can cancel GPS where they believe the contractor "knew or should have known" about fraudulent activity in their supply chain. The bar means you cannot even apply to recover GPS for five years. For businesses that rely on gross payment to manage cash flow, this is potentially catastrophic. Rigorous due diligence on every subcontractor is now essential, not optional.
Businesses and directors can face penalties up to 30% of lost tax for "knew or should have known" fraud connections. This personal exposure extends beyond corporate assets to directors' homes, savings, and personal property. The risk makes professional verification and record-keeping critical for every contractor, regardless of size.
We represent you during HMRC compliance checks, correcting historical errors and managing disclosures proactively. If HMRC identifies discrepancies in your CIS returns, we respond with documented evidence, clear explanations, and negotiated resolutions. We do not panic. We do not hide. We engage professionally and protect your interests.
Our proactive compliance reviews identify weaknesses before HMRC does. We examine your verification records, deduction calculations, return filings, and payment statements. We spot patterns that might trigger enquiries and correct them before they become problems.
Avoid costly penalties and reclaim every pound you’re owed. Our specialist CIS accountants keep contractors and subcontractors compliant, organised, and financially secure.
We audit your current registration, returns history, and compliance status. We identify immediate risks, historical errors, and missed refund opportunities. No obligation, no hard sell, just clear findings.
We register you with HMRC if needed, correct historical errors in previous returns, and configure your accounting software with CIS modules that match your actual workflow. We clean up the past so you start from the correct position.
Verification of new subcontractors, correct deduction calculations, CIS300 filing by the 19th, and payment statement issuance. Every month, on schedule, without fail. You receive confirmation of filing and summary reports for your records.
Self-assessment returns for subcontractors, refund claims with full expense documentation, and forward planning for the next tax year. We ensure you start April with a clean position, maximum recovery, and no surprises.
CIS is HMRC's tax deduction scheme for construction work. Contractors must deduct tax from subcontractor payments at 20% for registered subcontractors or 30% for unregistered ones. These deductions count as advance payments toward the subcontractor's tax and National Insurance liabilities.
Registration is voluntary but strongly recommended. Unregistered subcontractors face 30% deductions versus 20% for registered. Registration requires a Unique Taxpayer Reference, verification of business status with HMRC, and ongoing compliance with scheme rules.
Registered subcontractors suffer 20% deductions. Unregistered subcontractors suffer 30%. Subcontractors with Gross Payment Status suffer 0% deductions but must meet strict criteria including turnover tests, compliance history, and business bank account requirements.
Automatic penalties apply regardless of excuse. £100 for one day late, £200 after two months, £300 or 5% of CIS deductions due at six months, and up to 100% of tax due at twelve months. Daily penalties of £10 per day apply after six months, capped at £900. Loss of Gross Payment Status and director personal liability may follow.
Yes, most CIS subcontractors overpay tax during the year because deductions exceed their actual tax liability. Self-assessment returns claim refunds by offsetting deductions against actual tax liabilities and claiming all allowable expenses.
Costs vary based on transaction volume, number of subcontractors, and service scope. Most contractors and subcontractors benefit from fixed monthly fees covering registration, monthly returns, and year-end support.
