Staying compliant with UK tax deadlines in March 2026 is very important for limited companies, contractors, freelancers and growing businesses. Missing even one deadline can result in HMRC penalties, interest charges and unnecessary stress.
If your company's financial year ended on 31 May 2025, your Corporation Tax payment deadline is 1 March 2026. In the UK, Corporation Tax must usually be paid 9 months and 1 day after your accounting year ends.
Important Points: Payment deadline is different from filing deadline. Tax must be paid even if return is not submitted yet. Late payment leads to HMRC interest charges.
HM Revenue & Customs updates Advisory Fuel Rates every quarter. These rates affect company car mileage reimbursement, fuel benefit calculations and private fuel adjustments. If your business provides company cars, update payroll and expense systems from March 2026.
If your VAT period ended on 31 January 2026, your VAT return and payment must reach HMRC by 7 March 2026. Under Making Tax Digital (MTD), VAT returns must be submitted digitally, businesses must keep digital records, and payments must be made electronically.
Late VAT Filing Can Cause: Penalties, interest, and compliance points. Review your VAT at least 7–10 days before the due date.
For businesses paying by post, this is the deadline for PAYE (employee income tax), National Insurance Contributions (NIC), and CIS deductions. This applies to payroll month ending 5 March 2026. Electronic payments are safer to avoid delays.
Construction businesses operating under CIS must submit their monthly return by 19 March 2026. You must report subcontractor payments, confirm deduction rates, and verify subcontractor status. Late CIS returns result in automatic penalties starting immediately.
If paying electronically, the deadline is 22 March 2026. Ensure funds clear before the deadline and don't wait until the last banking hour. Late payment triggers interest from HMRC.
If your accounting year ended on 31 March 2025, your Corporation Tax return filing deadline is 31 March 2026. The return must include statutory accounts, CT600, online filing in iXBRL format. Late filing penalties increase over time.
If your company owns high-value residential property in the UK and filed an ATED return, this is the last date to amend it. ATED compliance is important for companies holding residential properties through corporate structures.
March includes multiple tax deadlines — Corporation Tax payment, Corporation Tax return filing, VAT return submission, PAYE and NIC payments, CIS returns, and ATED amendments. Because these dates fall close together, businesses often miss one deadline.
To manage March 2026 accounting dates smoothly:
RH KPO Services helps UK limited companies, contractors and accounting firms stay ahead of every deadline with accurate, timely outsourcing support.
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