Tax Diary August/September 2026

1 August 2026 – Due date for Corporation Tax due for the year ended 31 October 2025.

19 August 2026 – PAYE and NIC deductions due for the month ended 5 August 2026. (If you pay electronically, the due date is 22 August 2026.)

19 August 2026 – Filing deadline for the CIS300 monthly return for the month ended 5 August 2026.

19 August 2026 – CIS tax deducted for the month ended 5 August 2026 is payable by today.

1 September 2026 – Due date for Corporation Tax due for the year ended 30 November 2025.

19 September 2026 – PAYE and NIC deductions due for the month ended 5 September 2026. (If you pay electronically, the due date is 22 September 2026.)

19 September 2026 – Filing deadline for the CIS300 monthly return for the month ended 5 September 2026.

19 September 2026 – CIS tax deducted for the month ended 5 September 2026 is payable by today.

Source:HM Revenue & Customs | 07-07-2026
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Aitch
Aitch is the visionary founder and CEO of CIGMA Accounting Ltd, a boutique accounting and tax advisory firm with offices in Wimbledon and Farringdon, London. With over a decade of experience, Aitch has built a reputation for strategic tax planning, complex HMRC compliance resolution, and innovative AI-powered accounting workflows that help SMEs, landlords, and high-net-worth clients streamline their finances. His expertise spans corporation tax, inheritance tax planning, R&D tax credit claims, capital allowances, and international tax matters, making him a trusted advisor for clients seeking to minimise tax liabilities while staying fully compliant. Aitch is passionate about bridging traditional accounting principles with cutting-edge digital solutions, allowing businesses to operate efficiently and future-proof their financial systems. Through CIGMA, he aims to make accounting smarter, faster, and more human-centric - empowering clients to focus on growth while staying ahead of regulatory changes.