A capital allowances claim is made in the company tax return, not by writing to HMRC. That sounds administrative and it has a consequence worth knowing: because the claim lives in the return, its time limit is the return's amendment window, and a claim missed at the time can usually still be made for a while afterwards but not indefinitely.
Where the claim is made
A company claims in its company tax return for the accounting period in which the expenditure was incurred, on the capital allowances pages of the CT600. There is no separate application and no advance approval. The company decides which allowance to use where an item qualifies for more than one, and it may claim less than the maximum: a company already at a loss often does exactly that, leaving the expenditure in the pool for a year when relief is worth more.
The time limits
The ordinary window is two years from the end of the accounting period, which is the period during which the return may be amended. After that, a claim for the period in question generally cannot be made, though expenditure that was never pooled can often still be brought into a later period's pool, which is the route most retrospective property claims take. This is why a capital allowances review of a building bought several years ago is usually still worth doing.
What makes a claim survive
Records that connect the money to the asset. An invoice that says refurbishment supports nothing; a schedule that allocates that invoice between the electrical installation, the sanitaryware, the general lighting and the decoration supports a claim on the parts that qualify. On a building this is what a capital allowances specialist actually produces, and the report is the deliverable rather than the tax figure. Not one of the specialists in this site's fee record publishes what that costs.
Questions people ask about claim capital allowances
How do I claim capital allowances?
In the company tax return for the accounting period the expenditure was incurred in, on the capital allowances pages of the CT600. There is no separate claim form and no advance approval.
How far back can I claim capital allowances?
The ordinary limit is the return amendment window, two years from the end of the accounting period. Expenditure never brought into a pool can often still be pooled in a later period, which is how most retrospective property claims are made.
Do I have to claim the maximum?
No. A company may claim less, leaving the balance in the pool for future years, which is common where the company is loss-making and the relief would be wasted.