Why Is My Corporation Tax Bill Higher Than Expected?

The accounts show a profit of £60,000 and you mentally calculate 19% as roughly £11,400. The actual CT bill comes in at £15,200. The gap is real and it happens regularly, because the profit figure in your accounts is not the same as the taxable profit HMRC uses to calculate the bill. Several adjustments sit between the two numbers, and if you have not been tracking them throughout the year, the final bill can feel like a surprise.

Disallowable expenses: what your P&L includes that HMRC does not

Your accounts are prepared under accounting standards which allow costs that tax legislation does not. The most common disallowable items:

• Depreciation: The annual charge for asset wear and tear in your accounts is never deductible for CT. It must be added back to arrive at taxable profit. Capital allowances replace it, but only to the extent you have actually claimed them.
• Client entertainment: Business entertainment costs (taking clients to dinner, corporate hospitality) are specifically disallowed under s45 CTA 2009. Staff entertainment, within limits, is allowable, but the line between the two is often blurred in the accounts.
• Fines and penalties: Any fine or penalty imposed by a regulatory body or government agency is disallowable. This includes parking fines, HMRC penalties, and Companies House late-filing fees.
• Non-trade legal costs: Legal fees relating to capital transactions or disputes that are capital in nature are not deductible against trading profits.
• Excessive remuneration: Salary payments to connected persons (including family members) that exceed a commercial rate for the work performed may be challenged by HMRC and partially disallowed.

The depreciation and capital allowances gap

This is the single biggest source of confusion between P&L profit and taxable profit. Depreciation in the accounts is calculated by the company under accounting standards, typically straight-line over the asset's useful life. HMRC ignores this entirely and substitutes a parallel system of capital allowances with its own rates.

If you bought a £30,000 piece of equipment and your accounts show £6,000 depreciation (over 5 years), you add the £6,000 back as disallowable. You then claim the capital allowance. If you claimed the Annual Investment Allowance, the full £30,000 is deductible in year one, giving you a much bigger tax deduction than the accounting depreciation, but only in the first year. In subsequent years, the CT deduction drops to zero while the accounts continue to show depreciation.

Companies that bought significant assets in a prior year and claimed AIA then often find their taxable profit in later years is higher than their accounting profit, because the depreciation continues in the accounts but there are no remaining capital allowances to claim.

Associated companies reducing your thresholds

If you or your co-shareholders control other companies, the £50,000 lower limit and £250,000 upper limit for marginal relief are divided between all associated companies. A director running two companies whose combined profit is £120,000 might assume the 19% small profits rate applies. With two associated companies, each company's lower limit is £25,000, both companies are in the marginal relief band and paying an effective rate above 19%.

This is one of the most commonly missed factors in CT estimates. Many directors do not consider their holding company, a dormant company, or a spouse's company as relevant, but HMRC's associated company rules catch all of these where the substantial commercial interdependence tests are met.

Prior year adjustments and HMRC amendments

A CT bill that is higher than the in-year calculation can sometimes be explained by adjustments to a prior year. This happens when:

• HMRC opens an enquiry into a prior year return and raises additional assessments
• The company amends its own prior year return after identifying an error
• A prior year loss that was carried forward is revised, changing the amount available to offset current year profits
• A prior year R&D claim is revised by HMRC

Profit higher than the management accounts suggested

Sometimes the explanation is simpler: the final accounts show higher profit than the year-end management accounts because adjustments are made in the audit or accounts preparation process. Accruals and prepayments are adjusted, stock is revalued, provisions are reversed, or invoices arrive after the period end but relate to the current year. Each of these increases the profit on which CT is calculated.

What to check if your bill seems wrong

If the CT bill you have received differs significantly from your expectation, work through these checks before assuming an error:

1. Obtain the detailed CT computation from your accountant and check the disallowance schedule
2. Confirm the number of associated companies used in the rate calculation
3. Check whether all capital allowance claims have been made and none have been missed
4. Verify that any prior year losses have been correctly applied
5. Check whether any prior year amendments or HMRC correspondence has affected the bill

Most unexpectedly high CT bills come down to one of the adjustments above. Identifying which one not only resolves the current confusion, it tells you where the planning opportunity sits for next year.