At a glance
- Separate the completed-year liability from advance instalments.
- Plan tax payments alongside customer receipts and supplier commitments.
- Review reserve estimates when trading or personal income changes.
A Self Assessment bill can be difficult to understand when it includes both tax for a completed year and an advance payment towards another year. For a business owner who budgets only for the profit just reported, that combination can make January feel unexpectedly expensive.
The solution is a clear explanation of the bill and a cash plan that keeps different periods separate. This guide explores payments on account, the records needed to understand them and a practical forecasting routine. It is especially relevant to sole traders whose cash is tied up in stock or customer credit. The budgeting examples are fictional and simplified. They do not calculate anyone's actual tax liability, which depends on the full tax position.
1. Understand what a payment on account represents
Payments on account are advance instalments towards the next Self Assessment tax bill. They are generally based on the preceding year's relevant liability, with two instalments usually equal to half that amount. HMRC's payments on account guidance explains the calculation and the exceptions.
Think of the payment as belonging to a future calculation, rather than as an extra charge simply added to the previous year's profit. The completed return establishes one position, while the advance instalments help fund another. The final calculation can then leave a balance to pay or an overpayment to consider.
That distinction matters when you are discussing cash with a partner or bookkeeper. A single bank payment may cover several elements, so calling the entire amount “last year's tax” obscures the planning problem. Ask for the bill to be explained by tax year and by purpose before building a reserve.
2. Check whether the rules apply to your bill
HMRC identifies exceptions where the previous year's tax owed was less than £1,000, or more than 80% of the tax owed was paid outside Self Assessment. Do not infer the answer from turnover, the balance in the bank or the tax deducted from one employment. The official guidance and your actual calculation are the starting points.
A business owner may have several income sources, deductions and payments affecting the overall position. This is why a rough statement such as “I already pay tax through my wages” is not sufficient to explain whether advance instalments arise. Collect the relevant employment and business information together so the calculation can be reviewed coherently.
If last year's position differed from this year's, make that change visible. A business beginning partway through a year, a change in employment or a different trading result can alter the planning conversation. The accountant needs the facts behind the comparison, not only two headline totals.
3. Read the statement before making assumptions
Locate the current Self Assessment statement or account information and identify which amounts it shows. Separate the tax year, balancing position, instalments already made and amounts still due. Where the account includes an adjustment, keep the correspondence explaining it. HMRC's tax bill overview describes how the calculation and account information can be accessed.
Do not rely solely on a screenshot of the largest figure. A statement is a record with dates and allocations, and the surrounding entries may explain why the total changed. If you have made a payment, retain its confirmation and reference so it can be connected to the account.
An accountant can help discuss the calculation, but they still need to know about recent payments or communications. A return prepared accurately from business records does not automatically reveal every movement in your tax account. Keeping the two evidence trails connected is a practical part of understanding what remains payable.
4. Put January and July into the cash calendar
The usual payments on account dates are 31 January and 31 July. A balancing payment may also fall due in January after the relevant tax year ends. Check the amounts and dates shown for your circumstances using HMRC's guidance rather than treating the calendar as a substitute for the statement.
Add these obligations to a cash calendar alongside rent, wages, supplier commitments, finance payments and other known outgoings. A tax date can coincide with an otherwise ordinary purchasing cycle. If that collision is only discovered in the final week, there may be less room to organise customer collections or adjust discretionary spending.
The calendar should show both the amount and the confidence level. A confirmed statement amount is different from an early estimate. Label each accordingly and review it as better information arrives. This prevents an approximate reserve from becoming an unquestioned figure that the business depends on.
5. A simplified illustration of the first payment cycle
Imagine that a fictional sole trader's relevant completed-year liability is £4,000, with no earlier instalments paid towards it. Assume, purely for this illustration, that payments on account apply and each is £2,000. The January cash requirement could then contain £4,000 for the completed year plus a £2,000 first instalment towards the following year. A second £2,000 instalment would be considered separately in July.
The £6,000 January total is not an assertion that the completed year's tax became £6,000. It combines two different purposes. In this simplified scenario, misunderstanding that distinction would cause the owner to reserve £4,000 and discover a £2,000 cash gap at payment time.
The example excludes complications such as amounts already paid, deductions, student loan liabilities and other adjustments. Use it to understand the structure of a cash conversation, not to estimate your own bill. Ask the accountant to identify the actual components and the periods to which they relate.
6. Build a reserve from an explained estimate
A tax reserve works best when it is based on an estimate you understand. Start with the likely payment position, existing funds set aside and the months available to build the remainder. Review the calculation when the trading outlook changes. Avoid selecting a percentage of every receipt simply because it sounds cautious.
For a wholesale business, receipts may include amounts that need to fund stock purchases, operating costs and other commitments. Moving cash into a reserve without considering those obligations can create pressure elsewhere. The reserve is one part of the cash plan, and the plan needs to reconcile with how the business actually trades.
A separate bank account may help distinguish money set aside from operating cash, but it is an organisational choice rather than a calculation of liability. Record transfers clearly and check the reserve balance periodically. The useful measure is whether the reserve matches the expected obligation, not whether the account exists.
7. Keep profit and available cash separate
Profit and cash answer different questions. A wholesaler can report a trading profit while customers have not yet paid, or while money has been committed to stock that has not been sold. Conversely, a bank balance can look healthy after borrowing without representing profit available for personal use.
Build a bridge between the management result and the cash forecast. Identify outstanding customer balances, stock purchasing commitments, supplier terms and finance movements. This explains why a profit estimate may not translate immediately into money available for a tax payment.
The accounting method and business structure affect how the tax position is calculated, so discuss those separately. The planning principle remains useful: do not assume a financial result and a bank balance are interchangeable. A payment reserve needs both an explained liability estimate and a realistic view of when cash will be available.
8. Use a rolling forecast with clear assumptions
A rolling cash forecast can begin with the opening bank balance, expected receipts and expected payments for each week or month. Put the tax amounts into the relevant periods. Keep the format simple enough that it can be updated using the records you actually maintain.
For receipts, distinguish confirmed payment dates from estimates. For payments, include committed orders as well as invoices already received. A forecast based only on current supplier statements may miss goods that have been ordered but not yet billed. Explain the assumptions behind large movements.
Use a cautious scenario alongside the central estimate. For example, consider what happens if a significant customer pays two weeks late or if a replacement stock order needs funding earlier than expected. These are planning scenarios, not predictions. Their value is showing where the payment calendar becomes tight enough to require attention before the deadline arrives.
9. Allow for seasonal trading patterns
Many businesses earn income unevenly. Food wholesalers may buy ahead of a seasonal sales period, while some self-employed clients have quieter months or payment gaps. A straight monthly average can hide these patterns. Use the trading history and current order information to understand where cash is likely to move.
Review the months leading up to a tax payment rather than only the payment month itself. A purchasing peak may consume funds earlier, and the corresponding customer receipts may arrive later. The forecast should show that sequence. Otherwise, a profitable season can still coincide with a cash shortage.
If the latest year is materially different from the previous one, explain why. A lost contract, a new product range or a change in customer terms can affect planning even before the final tax calculation is ready. The accountant can discuss the relevant work more usefully when those commercial changes are described rather than hidden inside an overall sales total.
10. Give personal drawings a place in the plan
For a sole trader, personal withdrawals can have a substantial effect on available cash. Record them clearly instead of allowing them to become unexplained bank items. A household budget can sit beside the business forecast so that both commitments are visible.
This is an accounting and planning distinction, not a judgment about personal spending. If the owner needs a regular amount for living costs, the cash plan should reflect it. Unexpected withdrawals are harder to accommodate when the same funds were assumed to cover suppliers or a tax reserve.
Compare the expected drawings with the business's cash generation and the timing of obligations. If the figures do not fit, recognise that early and discuss the available options with the appropriate advisers. Moving a payment date in a spreadsheet does not change a real commitment. A useful forecast makes the pressure visible rather than disguising it through optimistic assumptions.
11. Discuss reductions only with supporting information
If you expect a lower liability, a claim to reduce payments on account may be relevant. HMRC provides a process in its reduction guidance. Reducing instalments too far can lead to interest on amounts that should have been paid, so the decision should be grounded in the expected tax position.
Prepare evidence for the discussion: current trading records, known income changes, employment information and a realistic forecast for the remainder of the year. A quieter month is not necessarily enough to establish a lower full-year liability. The effect of other income sources also needs consideration.
Keep the forecast and the reason for any change with the tax file. If circumstances improve later, revisit the estimate rather than leaving a reduction based on an outdated position. This makes the planning decision traceable and helps avoid confusing a short-term cash problem with a genuine change in the expected liability.
12. Plan the payment process as well as the amount
Once the amount is understood, check the payment route, reference and processing time that apply. HMRC sets out the available methods in its Self Assessment payment guidance. An agreed reserve is only useful if the payment is made correctly and can be connected to the account.
Keep the payment confirmation and reconcile it with the bank record. If an amount is not reflected as expected, the reference and date help investigate the difference. Avoid making an unverified second payment simply because the first has not appeared immediately.
If payment looks unaffordable, raise the issue promptly and check the options directly with HMRC or your adviser. Do not assume that completing a return automatically creates a payment arrangement. An early conversation gives a clearer basis for discussing the obligation, available funds and practical steps.
13. Set a regular tax planning check-in
A short quarterly review can compare the reserve with the latest estimate and upcoming dates. Review the business result, expected income outside the business, cash forecast and any HMRC statement changes. The conversation can be brief if the underlying information is organised.
Record the actions that follow. Perhaps the reserve needs increasing, a missing document needs obtaining or a customer balance needs attention. Assign a person and date to each action. This turns the review into a working routine rather than an observation that the figures might be tight.
The reporting frequency should fit the business and the agreed scope. A complex wholesale operation may need more frequent cash information than a small activity with stable income. The useful question is what information will allow decisions to be made in time. More reporting is not automatically better if the records cannot support it or nobody acts on the result.
14. What to bring to the accountant
Provide the latest return and tax calculation, current statement, payments already made and any relevant correspondence. Add the business records, other income information and a short explanation of changes. If you have a forecast, label the assumptions and separate confirmed commitments from estimates.
For a wholesale business, explain stock purchasing, customer terms and major supplier dates. These details help connect the tax discussion with the cash available to meet it. If the records are incomplete, list the gaps rather than waiting until everything looks finished.
Our Self Assessment preparation guide provides a broader record checklist. You can also explore management accounting support where regular performance and cash information would be useful. The tax calculation and management reporting can be discussed together, with their purposes and responsibilities kept clear.
15. A practical reserve routine for the next twelve months
Begin by recording the next confirmed tax payment and the funds already reserved. Then add the following payment date and an explained estimate. Compare both with the cash forecast. This establishes a starting position that can be reviewed as information improves.
At each review, update the trading outlook, expected customer receipts, supplier commitments and reserve movement. Check whether the assumptions behind the tax estimate still make sense. Document the changes rather than rewriting the previous estimate with no explanation.
At year end, connect the final accounts and return to the instalments already made. Compare the resulting balance with the reserve and identify why any difference arose. This learning helps improve the next cycle. A large difference may reflect changed profits, incomplete forecasts or a misunderstanding of the original bill, and each needs a different response.
16. Connect the tax question to the business context
Payments on account become more manageable when the calculation, statement and cash plan tell a consistent story. Good preparation does not remove a liability, but it can help you understand what it represents and when funds need to be available. That understanding is valuable before a busy purchasing period or a change in business activity.
CRV Gudka & Co supports businesses and private clients from its Edgware office, with a dedicated team and a wholesale and food-import accountancy specialism. We can discuss relevant tax work, bookkeeping and management information as connected areas of support.
When you contact the practice, explain the payment year involved, the current records and the question you need answered. The team can then discuss a scope that addresses the actual position. A clear explanation and a realistic routine provide a better foundation for planning than treating every January bill as an unexpected event.
About this guide: prepared for CRV Gudka & Co's accounting journal. Official guidance was checked on 10 October 2026. Examples are illustrative. The work and treatment applicable to you depend on your circumstances and the engagement agreed with the practice.
