How to Pay Your Self Assessment Tax Bill – Everything You Need to Know (May 2025)

As a business owner or self-employed individual, staying on top of your Self Assessment tax bill is crucial — not just to meet deadlines, but to protect your finances, avoid fines, and maintain peace of mind.

Even though the main payment deadline is 31st January, there are important steps you may need to take right now, especially with the second payment on account due by 31st July. Whether you're catching up, filing early, or budgeting ahead — this guide from MCC Partners gives you everything you need to know.

Why Paying Attention to Your Self Assessment Tax Bill Matters Right Now

There’s a common misconception that you only need to think about Self Assessment tax in January. But in reality, May is one of the best times to act, especially for:

• Business owners expecting a second payment on account due 31st July
  
  

• Those who want to file early for the new 2024–2025 tax year
  
  

• Anyone who missed the January 31st deadline and now faces interest or penalties
  
  

By getting ahead now, you can manage your cash flow, avoid stress, and stay in control of your finances.

When Do You Have to Pay Your Self Assessment Tax Bill?

Do you have to pay Self Assessment tax by 31st January?

Yes — the main deadline to pay your Self Assessment tax bill is 31st January following the end of the tax year (which ends on 5th April). For example, for the 2023–2024 tax year, the payment deadline is 31st January 2025.

However, if you're required to make payments on account, you’ll also need to make a second payment by 31st July — which is why May is a key time to prepare.

What Is the Deadline for Paying Tax at HMRC?

• 31st January – Pay any tax owed for the previous tax year
  
  

• 31st July – Pay your second payment on account (if applicable)
  
  

How to Pay Your Self Assessment Tax Bill

Once you've filed your return and know how much you owe, you can pay your bill using several HMRC-approved methods:

Accepted Payment Methods

• Bank transfer (Faster Payments, CHAPS, Bacs)
  
  

• Online via debit or corporate credit card
  
  

• Direct Debit (must be set up in advance)
  
  

• By cheque through the post
  
  

• At your bank or building society (with HMRC payment slip)
  
  

What Information Do I Need?

You’ll need your 11-character payment reference – this is your UTR number followed by ‘K’.

💡 MMC Tip: Bank transfer is fast, reliable and typically processed within 24 hours.

Can I Pay My Tax Bill in Instalments?

Yes — HMRC allows you to set up a Time to Pay arrangement if you’re unable to pay the full amount on time.

Will HMRC Give Me Time to Pay?

If you owe less than £30,000, you can usually set up a payment plan online. For larger amounts or more complex situations, contact HMRC directly or speak to us at MMC Partners for support.

What Happens If I Pay My Self Assessment Tax Late?

If you miss the payment deadline, HMRC will begin applying penalties and interest — and they increase the longer you delay.

What Is the Penalty for Late Payment?

• £100 fixed penalty if your return is up to 3 months late
  
  

• Additional £10 per day from 3 to 6 months late (up to £900)
  
  

• 5% of tax owed added at 6 and 12 months late
  
  

How Much Does HMRC Charge for Late Tax Return?

In addition to the above penalties, interest is charged daily on late payments at the HMRC interest rate.

How Late Can I Pay My Tax Bill?

You can technically pay at any time, but once you’re past the 31st January deadline, interest and penalties begin to accrue. If you're struggling to pay, it's better to set up a plan early rather than ignoring it.

How to Calculate Late Filing Penalty

HMRC’s penalties are structured as follows:

• £100 flat fee for missing the deadline
  
  

• After 3 months: £10 per day for up to 90 days
  
  

• After 6 months: Additional 5% of unpaid tax
  
  

• After 12 months: Further 5% of unpaid tax
  
  

Use HMRC’s penalty calculator or speak to MCC Partners to assess your current position.

What Is the Late Fee for Updated Return?

If you need to update your return after submission:

• There’s no charge if corrected within 12 months of the original deadline.
  
  

• After 12 months, it could be considered a deliberate error, which may lead to penalties of 15% to 100% of the extra tax owed.

Understanding Payments on Account (Especially for July)

Payments on account are advance payments towards your next tax bill. They apply if your previous year’s tax bill was over £1,000 (and less than 80% was collected via PAYE).

Key Payment on Account Dates

• 31st January – First payment
  
  

• 31st July – Second payment
  
  

Each is typically 50% of your last bill.

Can I Reduce My Payment on Account?

Yes — if your income is expected to be lower, you can apply to reduce payments via your HMRC account. But be careful: underestimating could lead to interest charges later.

How Far Back Can HMRC Go for Underpaid Tax?

HMRC can investigate up to:

• 4 years for innocent errors
  
  

• 6 years for carelessness
  
  

• 20 years for deliberate tax evasion
  
  

That’s why it's crucial to keep accurate records and seek professional advice.

Need Help with Your Self Assessment Tax Bill?

At MMC Partners, we support business owners, landlords, contractors, freelancers and company directors with:

• Early and accurate Self Assessment returns
  
  

• Payment planning and reminders
  
  

• Dispute resolution and penalty appeals
  
  

• HMRC communication and Time to Pay setups
  
  

📞 Get in Touch

Avoid the stress of last-minute tax filing. Speak to MCC Partners today.

Call: 01474 619 990
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Website:www.mccpartners.co.uk