How to keep business tax reserves separate from spendable cash

Tax reserves are not a tax calculation method. They are a cash-control method: money is moved aside during the year so a future HMRC payment does not compete with payroll, suppliers or growth spending at the last minute.

Start with the actual payment dates, not a vague annual estimate

Build a tax calendar first. GOV.UK states that companies with taxable profits up to £1.5 million normally pay Corporation Tax nine months and one day after the end of the accounting period, while larger companies can fall into instalment rules. VAT returns are usually due one calendar month and seven days after the end of the VAT accounting period, and the payment normally has the same deadline.

Sole traders and partners using Self Assessment usually face a 31 January balancing-payment deadline and may also make payments on account on 31 January and 31 July. Put the dates into the cash-flow forecast months in advance. The purpose of a reserve is to make the eventual payment routine, not to discover the liability when the deadline is already close.

Choose a reserve method that follows the way tax is generated

There is no universal percentage that every business should move aside. The appropriate reserve depends on taxable profit, VAT position, payroll, reliefs and business structure. A percentage transfer can still be useful as a control, but it should be based on the accountant's or tax software's estimate rather than a number copied from another company.

For example, a limited company might transfer a fixed share of monthly estimated taxable profit into a Corporation Tax reserve and update the percentage quarterly when management accounts are reviewed. A VAT-registered retailer may move the VAT element of daily or weekly receipts into a separate pot after allowing for expected input VAT. The method should follow the liability rather than treating all cash in the bank as economically identical.

Treat VAT collected from customers as money with a future job

VAT creates a common cash-flow trap because the business receives the money before it must pay HMRC. A company with strong sales can therefore look cash-rich immediately after a VAT period ends even though a substantial part of that balance is already committed. The usual VAT deadline is one calendar month and seven days after the accounting period, so the gap is long enough for the money to be spent accidentally.

Suppose a business ends a quarter expecting £28,000 of VAT payable after deducting input VAT. If that £28,000 remains mixed with general working cash, management may approve stock, bonuses or equipment purchases against a balance that is not truly free. A separate reserve makes the obligation visible. Reconcile it to the actual return before payment so the reserve does not become a substitute for correct VAT accounting.

Plan Corporation Tax from estimated taxable profit, not the year-end bank balance

Corporation Tax is based on taxable profits, which are not the same as cash in the bank. Capital allowances, disallowable expenses, losses and other tax adjustments can change the liability. That is why the reserve should be linked to a tax estimate, not simply to revenue or month-end cash. Update the estimate after material changes such as a strong quarter, a large asset purchase or a revised profit forecast.

The payment deadline is usually earlier than the Company Tax Return filing deadline. GOV.UK states that the return is generally due 12 months after the accounting period ends, while the Corporation Tax payment is normally due nine months and one day after the period. A company that waits for the filing deadline before thinking about payment has left the cash decision too late.

Allow for payments on account when reserving tax as a sole trader or partner

Self Assessment can create a larger January cash requirement because the bill may include both a balancing payment for the previous tax year and the first payment on account for the current year. GOV.UK also lists 31 July as the usual second payment-on-account date. A new self-employed person can therefore face a first major payment that feels much larger than one year's simple tax percentage.

Reserve against the expected Self Assessment statement rather than guessing from turnover. If profits change materially, discuss the payments-on-account position with an accountant or use HMRC guidance before reducing them. Reserving too little creates a cash problem; reserving too much is less dangerous but can unnecessarily restrict working capital if the estimate is never reviewed.

Decide where to hold tax reserves without creating access risk

The reserve needs to be liquid enough to reach HMRC by the deadline. That often makes an instant-access or suitably timed notice account more appropriate than locking the full amount away for a long term. Check transfer limits and withdrawal notice periods before chasing a slightly higher rate. A tax reserve that cannot be accessed on time has failed its main purpose.

If the reserve becomes large, also consider deposit protection and banking concentration. FSCS protection applies subject to eligibility and authorised-firm rules, so check the legal bank and shared banking licence rather than relying only on the brand. Keep the control simple: the reserve should be visible, reconciled and hard to spend casually without making the actual tax payment difficult.