Landlord Self Assessment: prepare the portfolio records before the deadline

Prepare your 2025/26 rental records for Self Assessment. Check October and January deadlines, late-filing penalties and the separate MTD regime.

For the 2025/26 tax year, the standard Self Assessment deadlines are 31 October 2026 for paper returns and 31 January 2027 for online returns. Payment is normally due by 31 January 2027. Portfolio landlords should plan the records review separately from submission: filing a return and paying the bill are distinct obligations. [1]

Confirm which deadlines apply

The tax year covered here ran from 6 April 2025 to 5 April 2026. HMRC publishes these standard dates:

31 October 2026: HMRC must receive paper returns.
30 December 2026: online filing deadline if requesting collection through a PAYE tax code, where eligible.
31 January 2027: online filing and the normal tax payment deadline.
31 July: a further payment date where payments on account apply. [1]

The notification deadline is 5 October 2026 where a person needs to tell HMRC they must complete a return under the conditions in its guidance. Not every new landlord automatically has the same filing obligation. If the deadline has passed before you act, check HMRC’s instructions promptly: a later deadline for submitting the return does not automatically move the payment deadline. [1]

Understand the late-filing exposure

For the standard Self Assessment regime described by HMRC, late filing starts with a £100 penalty. After three months, daily £10 penalties can apply up to £900. At six months, a further 5% of tax due or £300 applies, whichever is greater; at twelve months, another such charge applies. [2]

Late payment has separate penalties and interest. Do not treat submitting the return as settling the bill. [2]

These are not universal rules for every current reporting obligation. HMRC publishes a separate penalty regime for Making Tax Digital for Income Tax. If you are within MTD, review that guidance for the relevant period rather than applying this ladder to quarterly updates. [3]

Build a review file for each owner and business

A practical preparation checklist is to:

1. Reconcile recorded rent with receipts and investigate differences. 2. Match expenses to supporting invoices and the relevant property. 3. Separate repairs, improvements and domestic-item replacements for review. 4. Retain finance statements and distinguish interest from loan repayments. 5. Confirm the ownership and income-allocation position. 6. Send unresolved questions to your accountant before the filing window closes.

These are workflow suggestions, not substitutes for HMRC’s rules on taxable income or deductible costs.

Use the late-filing penalty calculator for an estimate under the regime it describes. It does not cover every penalty scenario or replace an HMRC notice.

LetSentry helps organise property income, expenses and receipts. It is a record-keeping tool, not HMRC-recognised MTD software, and does not submit tax returns. Explore LetSentry’s buy-to-let portfolio tools alongside your existing accountant or filing arrangements.

Official sources

1. GOV.UK: Self Assessment deadlines 2. GOV.UK: Self Assessment penalties 3. GOV.UK: penalties for Making Tax Digital for Income Tax

General information, not individual tax advice. Check your HMRC notices and the rules for your reporting period.

Sources: - GOV.UK: Self Assessment deadlines (accessed 2026-09-21): https://www.gov.uk/self-assessment-tax-returns/deadlines - GOV.UK: Self Assessment penalties (accessed 2026-09-21): https://www.gov.uk/self-assessment-tax-returns/penalties - GOV.UK: penalties for Making Tax Digital for Income Tax (accessed 2026-09-21): https://www.gov.uk/guidance/penalties-for-making-tax-digital-for-income-tax - Finance Act 2009, Schedule 55: penalties for failure to make returns (accessed 2026-09-21): https://www.legislation.gov.uk/ukpga/2009/10/schedule/55

Published: 2026-09-21.

Last reviewed: 2026-09-21.

General summary; not legal advice.