Cannot Pay Your Self Assessment Tax Bill? What Happens and What to Do

When does your Self Assessment tax bill need to be paid?

The normal Self Assessment payment dates are:

Payments on account are advance payments towards the following year’s tax bill. They normally apply when your previous Self Assessment liability meets HMRC’s relevant conditions.

For example, someone completing their 2025/26 Self Assessment return will normally need to pay any balancing amount by 31 January 2027.

You can read more about preparing a return and the relevant dates in Real Key Accountancy’s sole trader tax return 2026/27 guide.

What should you do if you know you cannot pay?

Finding out that you cannot afford a tax bill can be worrying, but there are practical steps you can take.

1. Submit your tax return anyway

Do not delay your Self Assessment return simply because you cannot pay.

If your online return is due on 31 January, submitting it late can create separate filing penalties. You could therefore turn one problem into two.

Submitting the return also establishes what you actually owe, which makes it easier to discuss payment with HMRC.

2. Check that the bill is correct

Before arranging finance or agreeing to instalments, make sure the tax calculation is based on accurate information.

Check that:

• all relevant income has been included;
• allowable business expenses have been recorded correctly;
• tax already deducted has been included where appropriate;
• previous payments have been allocated correctly;
• any payments on account have been taken into consideration.

Do not reduce a legitimate tax liability simply because it is unaffordable. However, there is little benefit in arranging payment for an amount that is wrong because records were incomplete.

Real Key Accountancy provides Self Assessment and bookkeeping support for sole traders, self-employed professionals and small businesses.

3. Pay what you reasonably can

If you cannot pay everything but can afford part of the bill, making a payment can reduce the outstanding balance.

Late-payment interest is charged on unpaid tax, so reducing the amount outstanding can reduce the interest that builds up.

However, do not leave yourself without money for essential living expenses simply to make an unplanned payment. If the problem is more significant, discuss it with HMRC.

4. Check whether you can use HMRC’s Time to Pay service

HMRC may allow an overdue tax bill to be paid through monthly instalments.

You can use HMRC’s online payment-plan service to check whether you qualify.

Self Assessment taxpayers who owe less than £30,000 may be able to arrange Time to Pay online if they meet the relevant conditions. HMRC confirmed that facility for the January 2026 Self Assessment payment cycle.

If the online service does not offer you a suitable arrangement, that does not necessarily mean no help is available. You can contact HMRC to discuss your circumstances.

What will HMRC ask when arranging Time to Pay?

If you cannot arrange a payment plan automatically, HMRC may ask about your finances.

Information can include:

• how much you can afford each month;
• your income;
• normal household or business spending;
• other taxes you need to pay;
• savings and investments;
• relevant assets.

HMRC says that if you have savings or assets available, it may expect you to use them to reduce the debt as far as reasonably possible.

The objective is normally to establish an arrangement that clears the debt as quickly as possible while remaining affordable.

Do not agree to a monthly figure simply because you feel pressured to resolve the call quickly. An arrangement that you cannot maintain may create another problem later.

Do you still pay interest with a Time to Pay arrangement?

Usually, yes.

A Time to Pay arrangement spreads the tax debt. It does not normally make the underlying tax or late-payment interest disappear.

As at 31 August 2026, HMRC’s published late-payment interest rate for the main taxes, including Income Tax, is 7.75%, effective from 9 January 2026. The rate is linked to the Bank of England base rate and can change.

Check HMRC’s current late-payment interest rates rather than assuming today’s rate will remain the same throughout your payment plan.

What penalties apply if you pay Self Assessment late?

For a 2025/26 Self Assessment balance normally due on 31 January 2027, the existing Self Assessment late-payment penalty system continues to apply.

Under that system, HMRC can charge a penalty equal to 5% of the unpaid tax at:

• 30 days after the payment deadline;
• six months after the payment deadline;
• 12 months after the payment deadline.

Interest is separate and can start building before those penalty points are reached.

An agreed Time to Pay arrangement can affect whether subsequent late-payment penalties arise. HMRC’s guidance makes it particularly important to contact them before relevant penalty trigger dates rather than waiting until months after the bill became due.

Are Self Assessment penalty rules changing?

Yes, but the timing matters.

New late-payment rules apply to people using Making Tax Digital for Income Tax from the relevant tax year. However, HMRC specifically confirms that someone required to use Making Tax Digital from 6 April 2026 will still have the existing penalty rules applied to their 2025/26 Self Assessment return and the 31 January 2027 deadline.

That distinction matters when reading information about the new penalty system.

What if the amount you cannot afford is a payment on account?

A large January Self Assessment bill can sometimes be surprising because it includes both:

1. the balancing payment for the year just ended; and
2. the first payment on account towards the following year’s liability.

A second payment on account is normally due on 31 July.

If you genuinely expect your following year’s tax liability to be lower, HMRC allows you to apply to reduce your payments on account.

However, cash-flow difficulties alone are not a reason to artificially reduce the estimated tax bill.

Your payments on account should only be reduced where you reasonably expect the underlying liability to fall. If you reduce them too far and later owe more tax, HMRC may charge interest on the underpayment.

Can you pay your Self Assessment bill through PAYE?

Some taxpayers with PAYE income have another option.

HMRC may collect qualifying Self Assessment tax through your PAYE tax code if all relevant conditions are met, including that:

• you owe less than £3,000;
• you already pay tax through PAYE;
• you submit an online tax return by 30 December, or a paper return by the applicable 31 October deadline.

There are additional restrictions, including limits designed to prevent excessive deductions from PAYE income.

Therefore, submitting your return early can sometimes give you more payment options.

What happens if you simply ignore HMRC?

A tax debt does not disappear because you stop opening the letters.

HMRC states that it will normally try to make contact and understand your circumstances before using enforcement powers. Where someone refuses to engage or no arrangement can be reached, however, HMRC can take further action.

Depending on the circumstances, HMRC may:

• use a debt collection agency;
• collect money from wages or pension payments;
• recover qualifying debts directly from bank or building-society accounts;
• take control of certain possessions and sell them;
• take court action;
• pursue bankruptcy as a final course of action.

These are serious measures, but they are not the normal first consequence of missing one payment by a few days.

The important difference is usually whether you communicate with HMRC and take reasonable steps to deal with the debt.

Example: a sole trader cannot afford the January tax bill

Example:

A self-employed consultant completes their 2025/26 tax return and discovers that £7,500 will be due on 31 January 2027.

They have £3,000 available but cannot find the remaining £4,500 without affecting essential household costs.

Instead of ignoring the bill, they:

1. check that the tax return and payments on account are correct;
2. pay the £3,000 they can afford;
3. check HMRC’s online Time to Pay facility;
4. arrange affordable instalments for the remaining balance;
5. continue setting money aside for future tax so the next payment does not create the same problem.

Interest may still apply to the unpaid balance, but acting early makes the situation far easier to manage than waiting for HMRC to begin recovery action.

How can you avoid the same problem next year?

Once the immediate tax bill is under control, look at why the shortfall happened.

For many sole traders, the difficulty comes from treating money received from customers as completely available to spend.

Your business bank balance is not necessarily your disposable income.

A better routine can include:

• keeping bookkeeping updated monthly;
• checking estimated profit regularly;
• calculating an estimated tax liability during the year;
• moving money into a separate tax savings account;
• reviewing expected payments on account;
• submitting your return early rather than waiting until January.

HMRC also offers a Budget Payment Plan for taxpayers who are up to date with previous Self Assessment payments. This allows weekly or monthly Direct Debit payments towards the next bill.

It is not a solution for an existing overdue balance, but it can make future January bills more manageable.

Common mistakes when you cannot pay a Self Assessment bill

Try to avoid these mistakes:

• Ignoring HMRC. Communication gives you more chance of agreeing a manageable solution.
• Not submitting the return. Filing late creates a separate penalty problem.
• Waiting for the first penalty before acting. Contact HMRC as early as possible.
• Assuming Time to Pay is interest-free. Late-payment interest normally continues.
• Reducing payments on account just because you need cash. Only reduce them where your expected liability genuinely supports the reduction.
• Agreeing to unaffordable instalments. A realistic arrangement is more useful than one you immediately break.
• Failing to budget for the next bill. An instalment plan for one year does not remove your future tax obligations.

Can an accountant help if you cannot pay your Self Assessment tax bill?

An accountant cannot guarantee that HMRC will approve a payment arrangement.

However, professional support can still be useful if you need to establish what you actually owe, bring bookkeeping up to date or understand why the bill is higher than expected.

Real Key Accountancy provides practical accounting, bookkeeping and Self Assessment support for sole traders, self-employed professionals and small businesses. You can speak to Real Key Accountancy about your accounting requirements if you need help getting your figures organised before dealing with HMRC.

Cannot pay your Self Assessment tax bill? Act early

If you cannot pay your Self Assessment tax bill, the problem is usually easier to deal with when you act before the debt grows.

Submit your return on time. Check the calculation. Pay what you reasonably can and contact HMRC about Time to Pay if you need longer.

For the 2025/26 tax year, the normal balancing-payment deadline is 31 January 2027. Late-payment interest can apply after the deadline, while penalties may follow if the balance remains unpaid.

Most importantly, do not ignore HMRC. A payment difficulty that may be manageable through an agreed arrangement can become much more serious if communication stops.