Self Assessment Deadlines 2027: Key Dates for UK Sole Traders

Missing a Self Assessment deadline can be costly. Here are all the key dates for UK sole traders in 2027, plus penalties to avoid.

Self Assessment Deadlines for 2027

Here are the important dates you need to remember for your Self Assessment:

What Are Payment on Account?

If your Self Assessment tax bill is over £1,000, HMRC will ask you to make advance payments towards the next year's tax bill. These are called "payments on account."

Each payment is roughly 50% of your previous year's tax bill:

• First payment: 31 January 2027
• Second payment: 31 July 2027

Penalties for Late Filing

Late filing penalties can add up quickly. Here's what you'll face if you miss the deadline:

• 1 day late: £100 penalty
• 3 months late: £100 + daily penalties of £10 per day (up to 90 days)
• 6 months late: Additional penalty of 5% of tax due
• 12 months late: Additional penalty of 5% of tax due

Late payment penalties also apply if you don't pay on time.

How to Avoid Missing Deadlines

• Set reminders: Put key dates in your calendar (now!)
• Start early: Don't leave categorisation until January
• Use digital tools: Censitio helps you categorise transactions throughout the year
• Save for tax: Set aside 20-30% of each payment for your tax bill

How Censitio Helps You Prepare

Censitio makes it easy to prepare your Self Assessment by:

• Tracking transactions — import CSV bank statements in seconds
• HMRC-ready export — download Excel summaries for Self Assessment
• Session history — save your work with a free account
• Desktop version — auto-categorization with HMRC rules

No more scrambling at the last minute.