We cannot work out the Corporation Tax for this return yet: what each message means

Short version. The “We cannot work out the Corporation Tax for this return yet” panel is a decision, not an error. It appears when we refuse to compute a figure we cannot check. Nothing is lost when it appears. Your figures stay saved, and the live estimate returns the moment the cause is fixed. The same rules block submission, so each message below is also telling you what would stop you filing. Find your message, read why we show it, and apply the fix.

Your AIA claim is above the limit

“The claim is declared as all Annual Investment Allowance, but the amount is above the AIA limit for this accounting period. The whole amount cannot be AIA, and this product cannot calculate or report the remainder as a writing-down allowance without the pool figures.” The panel shows your amount and the limit for your exact dates.

Why. The Annual Investment Allowance has an annual limit, and a claim above it is refused rather than capped. The excess would be a writing down allowance computed from pool figures we do not hold, so capping the claim would file a claim you never made.

The limit is reduced day by day for an accounting period shorter than twelve months, and a period that straddles one of the changes gets a blended limit. We work out the exact limit for your dates before we compare your figure against it.

The fix. Check the amount first, because the usual cause is a typo such as an extra zero. If the figure is wrong, correct it in the wizard and the estimate returns. If the company genuinely spent more than the limit on qualifying equipment, the return needs pool computations we do not produce, so please use an accountant for this period. Our capital allowances article explains what belongs in the AIA field.

A trade and a property business, one claim

“Company carries on both a trade and a property business and has a capital-allowances claim that has not been confirmed as belonging wholly to the trade. We file one figure against the trade, which can overstate the tax if part of it relates to the property business.”

Why. A trade claim and a property-business claim go in different boxes on the Corporation Tax return, and the split changes the tax. We do not guess the split for you.

The fix. Answer the “Does the whole claim belong to the trade?” question in the wizard. If part of the claim relates to the property business, see capital allowances for landlords for how the two claims are kept apart.

Plant inside a let home, or use not confirmed

Two messages share one cause. The first is a refusal:

“Capital allowances are not available for plant used inside an individual let dwelling (CAA 2001 s.35), so this claim cannot be filed. Plant in commercial property or serving the shared parts of a building does qualify.”

The second appears when we have not been given an answer at all:

“This property company has a capital-allowances claim whose eligibility has not been established: plant inside an individual let dwelling does not qualify, and we have not been told what the plant is used for.”

Why. The law bars plant and machinery allowances for items used inside a home the company lets out, so a claim that includes them would be wrong, and a claim whose use we do not know might be. The common parts of a block of flats qualify, but the shared areas of an HMO or a house share count as inside the home, so they do not.

The fix. Answer the question about what the plant is used for truthfully, and remove any ineligible items from the claim. See capital allowances for landlords for which items a property company can claim.

The building was not confirmed in use all period

“A structures and buildings allowance accrues only while the building is in qualifying use, and we have not been told it was in qualifying use for the whole period. We cannot check a part-period claim, so we cannot file this return.”

Why. The allowance accrues day by day, and only while the building is in qualifying use. We block the return when the whole-period question is answered “No, or not sure”, and also when it has not been answered at all, because in both cases we cannot check the claim.

The fix. Answer the whole-period question in the wizard. If the building genuinely was not in qualifying use for the whole accounting period, the claim needs a day-count apportionment we cannot check, so please use an accountant. See the structures and buildings allowance article for what qualifying use means.

Zero-emission car outside the relief window

“The 100% allowance for new zero-emission cars covers expenditure from April 2021 to 31 March 2027, so it cannot be claimed for this accounting period.”

Why. The 100% first year allowance for a new, unused, fully electric car is time-limited by statute, and your accounting period sits outside the window, so no part of the period can carry the claim.

The fix. Remove the figure from the zero-emission field for this period, and see company cars and capital allowances for what a car bought outside the window can claim instead.

A first period over 12 months with a claim

“A first accounting period longer than 12 months is filed as two returns, and capital allowances or balancing charges belong to the specific return covering the purchase or sale, which we cannot work out. We cannot file this year for you. Please use an accountant or other software for this first period. Do not simply leave the claim out, because unclaimed allowances can be lost.”

Why. A company’s first accounts often cover more than twelve months, and HMRC requires two Corporation Tax returns for that year. Each allowance or balancing charge belongs to the return whose dates cover the purchase or the sale, and we do not hold the dates needed to place them.

Do not delete the claim to get past this message. The Annual Investment Allowance can only be claimed in the period of the expenditure, and an unclaimed structures and buildings allowance can be lost for good, as HMRC explains in CA94650. Removing the claim would clear the panel and cost the company relief it is entitled to.

The fix. Use an accountant or other software for this first year, and come back to us for the next one. See filing a long first accounting period for how the two returns work.

Other messages

Three further messages appear less often:

After you fix it

The estimate recomputes live as you edit, so there is nothing to resubmit and no button to press. The moment the cause is fixed, the panel disappears and the Corporation Tax figure comes back on its own.

Messages that appear at the filing stage, after you send the return to HMRC, are a different thing with a different page. See CT600 filing errors for those.

This article is general guidance, not tax advice. Where a message points you to an accountant, that is a genuine boundary of what we can check rather than a formality, and an accountant can file the claim we cannot. If you are not sure which message you are seeing, get in touch and we will look at it with you.