Tax Diary August/September 2026
Staying on top of tax deadlines matters for every business. Therefore, we have set out the key dates for the coming two months. Use this Tax Diary August/September 2026 to plan your payments and filings well in advance.
Why deadlines matter
Firstly, missing a deadline can trigger interest charges and penalties. Consequently, cash flow may take a hit at the worst possible moment. Furthermore, late filings can attract HMRC scrutiny. So, marking dates in your calendar now saves stress later.
Key dates for August 2026
Throughout August, several deadlines fall due. In particular, watch out for the following:
- 1 August 2026 – Due date for Corporation Tax for the year ended 31 October 2025.
- 19 August 2026 – PAYE and NIC deductions due for the month ended 5 August 2026. However, if you pay electronically, the due date extends to 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.
Therefore, plan your August cash flow around these key dates. Moreover, set reminders a few days in advance.
Key dates for September 2026
Similarly, September brings its own round of obligations. Specifically, note the following:
- 1 September 2026 – Due date for Corporation Tax for the year ended 30 November 2025.
- 19 September 2026 – PAYE and NIC deductions due for the month ended 5 September 2026. However, electronic payers have until 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.
Consequently, September’s mid-month deadline mirrors August’s pattern. So, once you build a routine, staying compliant becomes far easier.
Tips to stay on track
Meanwhile, a few simple habits can keep you ahead. For example, consider the following:
- Set diary reminders one week before each deadline
- Reconcile your payroll records monthly
- Review CIS deductions before filing
- Pay electronically to gain the extra three days
Additionally, speak to your accountant early if cash flow looks tight. After all, HMRC prefers early communication over silence.
Speak to our team
Need help meeting these deadlines? Get in touch with our team today for tailored support. We will happily review your obligations and keep you fully compliant throughout the Tax Diary August/September 2026.
