August 13, 2026

A Beginner's Guide to Self-Assessment Tax Returns

Learn the essentials of filing your self-assessment tax return, from registration to payment, with tips to simplify the process.

SE

Smart Expense Team

family — 2 min read

Overview

Filing your first self-assessment tax return can seem daunting, but understanding the process can make it much easier. In this guide, we’ll walk you through the steps you need to take to ensure you’re prepared and organized.

What is Self-Assessment?

Self-assessment is a method used by HM Revenue and Customs (HMRC) for individuals to report their income and calculate their tax liability. If you're self-employed, earn additional income, or meet certain conditions, you’ll need to file an annual tax return.

Automate this with Smart Expense

Smart Expense turns receipts and bank alerts into categorized spend automatically.

Get Started Free →

Do You Need to File a Self-Assessment?

Many individuals have their taxes automatically deducted from their wages, but if you fall into any of the following categories, you may need to file:

  • You are self-employed with an income over £1,000.
  • You earn additional income from property, savings, or investments.
  • You receive income from abroad or have capital gains.

Check your eligibility with HMRC if you're unsure.

Registering for Self-Assessment

If you're new to self-assessment, the first step is to register with HMRC for a Unique Taxpayer Reference (UTR). It's essential to do this as soon as possible, ideally by 5 October after the tax year ends. Once registered, you’ll receive your UTR, which you'll need to file your return.

Gathering Your Documentation

Before filing, you’ll need to collect relevant documents. This includes:

  • Payslips and your P60 if employed.
  • Invoices and receipts if self-employed.
  • Bank statements for all income sources.

Keeping these organized will make the filing process smoother.

Filing Your Tax Return

Once you have all your documents, you can complete your self-assessment tax return online through HMRC’s portal. If you're using Smart Expense, you can streamline this process: simply use the Email Reader feature to scan your transactional emails and automatically create expense entries, or use the to upload receipts directly into the app. This helps you keep accurate records without manual entry.

Paying Your Tax Bill

After submitting your return, HMRC will send you a statement detailing what you owe. Ensure you pay any tax due by the deadline (usually 31 January following the tax year). Smart Expense can assist you in tracking any income and expenses to help you budget for your tax payments efficiently.

Automate your expense process with Smart Expense Capture receipts, email invoices, and approvals in one place.