Self Assessment: When to Register, File & Pay
- josie139
- Oct 23
- 4 min read
If you're self-employed, a sole trader, or earn income outside of PAYE, understanding self-assessment deadlines is essential. Missing key dates can result in penalties, interest charges, and unnecessary stress. At Josie Dayment Bookkeeping Ltd, we're here to guide you through the process and ensure you stay on top of your tax obligations.
Let's break down the three critical stages of self-assessment: when to register, when to file, and when to pay.
When to Register for Self Assessment
The first step in your self-assessment journey is registration. You need to register with HMRC if any of the following apply to you:
You're self-employed and earned more than £1,000 in the tax year
You're a partner in a business partnership
You receive income from renting out property
You have untaxed income from savings, investments, or dividends above certain thresholds
You're a company director (unless it's a non-profit organisation and you don't get paid)
Your total income is over £100,000
You need to pay capital gains tax on assets you've sold
Registration Deadline
You must register by 5 October following the end of the tax year in which you became self-employed or first needed to complete a tax return. For example, if you started self-employment in the 2024/25 tax year (which runs from 6 April 2024 to 5 April 2025), you need to register by 5 October 2025.
Once registered, HMRC will send you a Unique Taxpayer Reference (UTR) number, which you'll need for filing your return. This can take up to 10 working days to arrive by post, so don't leave it until the last minute.
When to File Your Self Assessment Tax Return
After registration comes the filing stage. You have two options for submitting your tax return, each with its own deadline:
Paper Tax Returns
If you prefer to file a paper return, the deadline is 31 October following the end of the tax year. For the 2024/25 tax year, this means your paper return must reach HMRC by 31 October 2025.
Online Tax Returns
Filing online gives you more time. The deadline for online submissions is 31 January following the end of the tax year. For the 2024/25 tax year, you have until 31 January 2026 to file online.
Most people choose the online option because it's faster, more convenient, and gives you an extra three months.
What You'll Need to File
Before you start your return, gather the following information:
Your UTR number and National Insurance number
Records of all income (invoices, bank statements, etc.)
Details of allowable business expenses
Information about any other income (employment, property, investments)
Records of pension contributions and charitable donations
Details of any benefits or tax credits received
When to Pay Your Self Assessment Tax Bill
Filing your return is only half the battle, you also need to pay any tax owed. Understanding the payment structure is essential to avoid penalties.
Payment Deadlines
There are typically two payment dates each year:
31 January – This is when you pay:
Any outstanding tax from the previous tax year (balancing payment)
Your first payment on account for the current tax year (50% of your estimated tax bill)
31 July – This is when you pay:
Your second payment on account for the current tax year (the remaining 50%)
What Are Payments on Account?
Payments on account are advance payments towards your next tax bill. HMRC uses your previous year's tax liability to estimate what you'll owe. If your tax bill was over £1,000 and you paid less than 80% through PAYE or other deductions, you'll need to make these advance payments.
If your income drops or you expect to earn less in the current year, you can apply to reduce your payments on account. However, if you reduce them too much and end up owing more, you may face interest charges.
Example Timeline
Let's say you're filing for the 2024/25 tax year:
By 5 October 2025: Register for self-assessment (if it's your first year)
By 31 October 2025: File a paper return (if applicable)
By 31 January 2026: File online return and pay any tax owed, plus first payment on account for 2025/26
By 31 July 2026: Pay second payment on account for 2025/26
What Happens If You Miss a Deadline?
HMRC takes deadlines seriously, and penalties can add up quickly:
Late filing: An immediate £100 penalty if your return is up to three months late, with additional charges for longer delays
Late payment: Interest charged on outstanding amounts, plus penalties of 5% at 30 days, 6 months, and 12 months late
The good news? These penalties are entirely avoidable with proper planning and organisation.
How Josie Dayment Bookkeeping Ltd Can Help
Navigating self-assessment doesn't have to be stressful. At Josie Dayment Bookkeeping Ltd, we take the complexity out of tax season by:
Ensuring you're registered on time
Keeping your records organised throughout the year
Preparing and filing your tax return accurately
Calculating your tax liability so there are no surprises
Reminding you of upcoming deadlines
Advising on allowable expenses to minimise your tax bill
We believe that staying on top of your tax obligations should be straightforward, not overwhelming. With the right support, you can focus on growing your business while we handle the paperwork.
Self-assessment is a responsibility that comes with being self-employed, but it doesn't have to be a burden. By understanding when to register, file, and pay, you can avoid penalties and stay in HMRC's good books.
Remember the key dates:
5 October: Registration deadline
31 October: Paper return deadline
31 January: Online filing and payment deadline
31 July: Second payment on account deadline
If you're feeling overwhelmed or simply want to ensure everything is handled correctly, get in touch with Josie Dayment Bookkeeping Ltd. We're here to make your self-assessment journey as smooth as possible. We can help you to:
Get your Xero up to date so you have all the information you need
Put you in touch with an accountant who can assist
Support you with Xero training
Or you can book a power hour with me to discuss and get some advice
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