A P800 and a PA302 Simple Assessment are different from a Self Assessment return. Check the year, income and tax already paid before acting. Query errors using the notice’s process and deadlines, especially if a second assessment or existing return could duplicate the same liability.
Why a letter may arrive now
HMRC's October 2026 agent update says tax calculations and Simple Assessments are being issued for tax owed on bank and building society interest earned in 2025/26. Some people may receive a second assessment after HMRC receives additional interest information.
That makes it important to check the figures rather than assume a new letter always represents a completely separate debt. Keep the earlier notice and evidence of any payment alongside the latest one.
Understand the document
A P800 explains an underpayment or overpayment under HMRC's reconciliation process. A Simple Assessment tells you about a liability HMRC has calculated without requiring an ordinary Self Assessment return for that calculation.
Neither document means every recipient must buy a tax-return service. Equally, a notice based on information HMRC holds may not capture every income source or reporting obligation you have.
Check for duplication
Compare employment, pensions, interest and tax deductions with your own statements. If a second Simple Assessment includes an amount already assessed and paid, check how the payment affects the remaining balance before paying again.
If you are already registered for Self Assessment for the same year, tell HMRC or your accountant. HMRC's current guidance addresses withdrawal of a Simple Assessment where Self Assessment applies; do not simply report or pay the same liability twice.
Raise errors promptly
HMRC says queries about an incorrect Simple Assessment should be raised within 60 days of the letter. Follow the notice for payment and challenge instructions rather than treating that period as a general extension to every deadline.
TaxSimba can review an enquiry and confirm whether a return or separately agreed assistance is appropriate. Send the complete notices and your supporting figures so the accountant can identify what HMRC has calculated and what, if anything, remains outside it.
Reconcile the notice to records already filed
Illustrative preparation example.
Put the P800 or PA302 beside the relevant income documents, tax paid and any Self Assessment calculation for that year. Identify the exact mismatch before contacting HMRC. Paying both figures without checking can conceal a duplicate assessment issue.
Check: What income or payment differs, and which notice process applies?
| Check | Practical action |
|---|---|
| What document and year is this? | Distinguish a P800 calculation, Simple Assessment and a Self Assessment notice. |
| Does it replace or overlap earlier figures? | Compare notices and payments so the same amount is not paid twice. |
| Are the income or tax figures wrong? | Raise the issue through the specified route and within the relevant notice deadline. |
Does a PA302 mean I must file a tax return?
Not by itself. Check whether other income or an existing Self Assessment requirement creates a separate duty.
Can I ignore a Simple Assessment because I file Self Assessment?
No. Tell HMRC about the overlap and follow the appropriate correction or withdrawal process.
Download a checklist for this guide
- Keep the complete notice and issue date.
- Identify tax year and document type.
- Compare source income and tax-deduction statements.
- List earlier notices and payments.
- Record query, payment and overlap-resolution instructions.