Payment on account (POA) catches many UK dentists off guard. This advance tax system requires you to pay HMRC in instalments based on your previous year's tax bill, rather than waiting until after you've filed your Self Assessment.

Whether you're an associate dentist with growing income or a practice owner managing multiple revenue streams, understanding payment on account rules is essential for proper tax planning and cash flow management.

When Payment on Account Applies

HMRC triggers payment on account when your Self Assessment tax bill exceeds £1,000 and less than 80% of that tax was collected through PAYE or other deductions.

For most dentists, this happens when:

  • Your self-employed income grows significantly
  • You start earning substantial private work alongside NHS contracts
  • You begin receiving practice profits as a partner or owner
  • You have investment income or rental properties

An associate earning £45,000 PAYE plus £35,000 self-employed income will likely face payment on account requirements. The self-employed element generates a tax bill that PAYE doesn't cover.

How Payment on Account Works

Payment on account splits your previous year's tax bill into two equal instalments, paid on 31 January and 31 July.

Here's the timeline:

  • 31 January: First payment on account plus any balancing payment for the previous tax year
  • 31 July: Second payment on account
  • Following 31 January: Final balancing payment (if needed) plus first payment for the new cycle

If your 2022-23 tax bill was £8,000, HMRC expects £4,000 on 31 January 2024 and £4,000 on 31 July 2024 as advance payments for 2023-24.

Calculating Your POA Payments

Each payment on account equals 50% of your previous year's Income Tax and Class 4 National Insurance. Capital Gains Tax and Class 2 National Insurance are excluded from the calculation.

HMRC calculates this automatically, but you can estimate your liability:

  • Take last year's total Income Tax
  • Add last year's Class 4 National Insurance
  • Subtract any tax already deducted (PAYE, dividends, etc.)
  • Divide the result by two

A practice owner with £12,000 annual tax liability would face POA payments of £6,000 each on 31 January and 31 July.

Reducing Payment on Account

You can reduce POA payments if you expect your current year's tax bill to be lower than last year's. This commonly happens when:

  • Your income has dropped significantly
  • You're taking a career break or reducing hours
  • Business profits are lower due to increased expenses or investments
  • You're changing from self-employed to PAYE employment

Submit a reduction claim through your online Self Assessment account or by calling HMRC. You'll need to justify the reduction with realistic income projections.

Be cautious with reductions. If you underestimate and still owe more than £1,000, HMRC charges interest on the underpayment from the original due dates.

Managing POA Cash Flow

Payment on account creates significant cash flow challenges, particularly the "triple hit" of 31 January when you pay:

  • Final balance for the previous year
  • First payment on account for the current year
  • Potentially a large combined sum

Effective strategies include:

  • Setting aside funds monthly rather than scrambling at deadlines
  • Using separate savings accounts for tax provisions
  • Planning major expenses around payment dates
  • Considering whether profit extraction timing affects your tax position

Common POA Mistakes

Dentists frequently struggle with these payment on account issues:

Forgetting the July payment: The 31 July deadline often catches people unprepared, especially if they've just dealt with January payments.

Over-reducing payments: Being too aggressive with reduction claims leads to penalties and interest charges.

Ignoring the system: Some dentists assume they can deal with tax "next year" without realising POA brings forward payment dates.

Poor record-keeping: Without proper tracking, it's difficult to estimate whether reductions are justified.

Getting Professional Help

Payment on account calculations can become complex, particularly for practice owners with multiple income sources or those going through practice acquisitions.

Consider specialist advice if you're:

  • Facing your first POA payments
  • Dealing with fluctuating income patterns
  • Managing practice transitions or partnerships
  • Unsure about claiming reductions

Professional guidance helps ensure you meet obligations while optimising cash flow and avoiding unnecessary penalties.