Self-Assessment Checklist: Documents You Need

22 September 2026

Filing your Self-Assessment tax return is much easier when you have everything you need prepared in advance. Hunting for documents after the fact is one of the most common reasons people either file late or make errors on their return. Whether you are employed with some additional income, a sole trader, a landlord or a company director, this checklist will help you gather everything you need before you or your accountant sits down to complete your return. If you are not yet sure whether you need to file at all, start with who needs to file a Self-Assessment tax return.

What Everyone Needs

Regardless of your circumstances, there are certain pieces of information you will always need to file a Self-Assessment return:

Your Unique Taxpayer Reference (UTR). This is the 10-digit number HMRC assigns to you when you register for Self-Assessment. It appears on your previous tax returns, HMRC correspondence and your HMRC online account.
Your National Insurance number. Found on your payslips, P60 or any letter from HMRC or the Department for Work and Pensions.
Your Government Gateway login. You will need your user ID and password to access your HMRC online account and submit the return.
Bank account details. If HMRC owes you a refund, you will need your sort code and account number to receive payment.

Checklist for Employees with Additional Income

If you are primarily employed and need to file a return because of additional income sources, gather the following:

P60. Your P60 shows your total employment income and the amount of tax deducted by your employer during the tax year. Your employer must provide this by 31 May following the end of the tax year.
P45 (if applicable). If you left employment during the tax year, your P45 will show your income and tax deducted up to that point.
P11D (if applicable). If you received any benefits in kind from your employer, such as a company car or private medical insurance, these will be recorded on your P11D.
Details of any other taxable income. This includes savings interest, dividends received, Child Benefit payments if you are subject to the High-Income Child Benefit charge, and any other untaxed income.
Gift Aid donation records. If you have made charitable donations through Gift Aid, keep records of the amounts and dates as these can reduce your tax liability.

Checklist for Self Employed Sole Traders

Self-employed individuals need a complete record of their business income and expenses for the tax year. Good bookkeeping through the year makes this straightforward:

Total business income. A summary or record of all sales invoices and other income received during the tax year.
Business expenses. Records of all allowable business expenses including office costs, travel, staff costs, professional fees, insurance, marketing and any other deductible expenditure.
Mileage log. If you use a personal vehicle for business journeys and claim mileage, a log of business miles travelled during the year.
Bank statements. Business bank statements for the full tax year to cross reference income and expenditure against your records.
Capital expenditure records. If you purchased any equipment, machinery or other business assets during the year, keep records of the cost and date of purchase as capital allowances may be available.
CIS deduction statements (if applicable). If you work in the construction industry and have had CIS deductions made from payments received, you will need your CIS deduction statements to claim this tax back.

Checklist for Landlords

Landlords need to declare all rental income and claim all allowable expenses for each property they let. Many landlords now also have to meet Making Tax Digital requirements:

Total rental income received. A record of all rent received from each property during the tax year.
Mortgage interest statements. Statements from your lender showing the amount of interest paid on any buy to let mortgages. Note that mortgage interest is not fully deductible for residential landlords but attracts a basic rate tax credit instead.
Letting agent fees and statements. If you use a letting agent, their annual summary will show income collected and fees charged.
Receipts for repairs and maintenance. Costs for repairs and upkeep of the property are deductible. Keep receipts for all work carried out.
Insurance premiums, council tax and utility costs. Any costs you pay as the landlord rather than the tenant may be deductible depending on the terms of the tenancy.

Checklist for Company Directors

Directors of limited companies typically receive income from both salary and dividends and may have additional income sources to declare:

P60 from your company. Showing your total director salary and PAYE tax deducted during the tax year.
Dividend vouchers. A record of all dividends declared and paid by the company to you during the tax year, including the dates and amounts.
P11D if applicable. If you received any benefits in kind through the company, such as private medical insurance or a company vehicle.
Loan account balance. If you have a director's loan account with the company, keep a record of any amounts outstanding as this can have tax implications.

When Should You Have Everything Ready?

The Self-Assessment deadline for online returns is 31 January. However, waiting until January to gather your documents creates unnecessary pressure and increases the risk of errors or missed items. A much better approach is to have everything compiled by October or November at the latest, giving you and your accountant plenty of time to prepare an accurate return well ahead of the deadline — and to plan for any payments on account that fall due.

At Affinity Associates Isaacs & Co, we work with our Self-Assessment clients throughout the year and contact them well in advance of the deadline to ensure records are gathered in good time. If you would like us to take care of your Self-Assessment return, get in touch and we will handle everything from start to finish.

Frequently Asked Questions

What do I need to file my Self-Assessment tax return?

At a minimum you will need your Unique Taxpayer Reference, your National Insurance number and your Government Gateway login. Beyond that, the documents you need depend on your income sources. Employees need their P60 and details of any untaxed income. Sole traders need income and expense records. Landlords need rental income and expense figures. Directors need their P60 and dividend vouchers.

How do I prepare for a Self-Assessment tax return?

Start by gathering all relevant income records for the tax year, including payslips, P60, bank statements, dividend vouchers and any rental income summaries. Then compile your expense records, ensuring you have receipts or statements to support any deductions you plan to claim. The more organised your records are before you start, the faster and more accurately the return can be completed.

What documents do I need for my tax return as a sole trader?

As a sole trader you will need a record of all business income received during the tax year, supported by invoices or sales records, and a breakdown of all allowable business expenses with receipts. You should also have your business bank statements, any capital expenditure records and, if you use a vehicle for business, a mileage log.

What documents do landlords need for Self-Assessment?

Landlords need a record of all rent received during the tax year, mortgage interest statements from their lender, letting agent statements if applicable, receipts for repairs and maintenance, insurance premiums and any other costs incurred in connection with the rental property. If the property is jointly owned, only your share of the income and expenses should be included.

When should I have my documents ready for my tax return?

Aim to have everything compiled by October or November, well ahead of the 31 January online filing deadline. Filing early gives you more time to check figures, address any queries and avoid the stress of a last-minute rush. It also means any tax refund you are owed will be paid sooner. If you are working with an accountant, check when they need your information to meet your agreed filing timeline.