Tax Diary March/April 2026

The Tax Diary March/April 2026 includes several important deadlines that affect companies, contractors and individual taxpayers. These dates arrive quickly, so early planning is essential. Careful preparation also helps prevent penalties and protects cash flow. Therefore, understanding each date in advance supports smoother financial management.

Corporation Tax deadlines you must monitor

The first major deadline occurs on 1 March 2026. Corporation Tax is due for companies with a 31 May 2025 year end. Paying on time protects compliance and avoids interest charges.

Another important deadline appears on 1 April 2026. This payment applies to companies with a 30 June 2025 year end. These dates may seem routine, yet they still require attention because they influence cash flow during the early spring period.

Self-Assessment deadlines in the Tax Diary March/April 2026

Self‑Assessment taxpayers must act before 2 March 2026. Any outstanding tax for 2024–25 paid after this date will attract a 5% surcharge. However, taxpayers can avoid this charge if they settle the liability by 1 April 2026. HMRC will also accept a time‑to‑pay agreement arranged by the same date. Therefore, early engagement remains vital.

PAYE and CIS responsibilities during March

Several PAYE and CIS obligations fall on 19 March 2026. Employers must pay PAYE and NIC for the period ending 5 March 2026. If they pay electronically, they have until 22 March 2026.

Businesses must also file the CIS300 return for the period ending 5 March 2026 by 19 March 2026. CIS tax deducted for the same period is also payable by this date. Coordinated payroll processes help ensure each requirement is met on time.

April PAYE and CIS deadlines you should prepare for

April continues the same pattern. PAYE and NIC for the period ending 5 April 2026 fall due on 19 April 2026, or 22 April 2026 if paid electronically. The CIS300 return for this period is also due on 19 April. CIS tax payments follow the same deadline. Therefore, early organisation helps prevent last‑minute issues.

Filing penalties you should avoid

A further deadline appears on 30 April 2026. Any 2024–25 Self‑Assessment tax return filed after this date will incur an additional penalty of £10 per day, for up to 90 days. Because these penalties escalate quickly, meeting this deadline is crucial.

Staying compliant through careful planning

Although these dates may seem familiar, they carry serious consequences for cash flow, compliance and financial stability. By planning ahead, reviewing internal processes and noting each deadline clearly, businesses and individuals can avoid penalties and maintain confidence in their tax obligations.