Calculate your hybrid rate of writing down allowance
Use this calculator to work out your hybrid rate of writing down allowance, if your accounting period includes the day the rate changed.
The main rate of writing down allowance changed from 18% to 14% on:
- 1 April 2026 for Corporation Tax
- 6 April 2026 for Income Tax
If your accounting period includes the date when the rate changed, you’ll need to work out a hybrid rate to use for that accounting period.
Your hybrid rate is worked out based on what how much of your accounting period is before the rate changed, and how much is after.
Before you start
You’ll need to know:
- which tax you pay
- the start date of your accounting period
- the end date of your accounting period
How to work out your rate manually
If you want to work out your hybrid rate, you should:
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Count the number of days in the whole accounting period.
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Count the number of days from the first day of the accounting period to the day before the rate changed, including the first day.
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Divide the days before the rate changed by the total number of days.
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Multiply the result by 18.
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Count the number of days from the day the rate changed to the end of the accounting period, including the day the rate changed.
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Divide the days from when the rate changed by the total number of days.
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Multiply the result by 14.
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Add the result from step 4 to the result from step 7. If the number has more than 2 decimal places, round up to 2 decimal places. This number is your hybrid rate.
Example
A company that pays Corporation Tax has an accounting period beginning on 1 January 2026 and ending on 31 December 2026.
In the accounting period there are:
- 365 total days
- 90 days before 1 April 2026
- 275 days after 1 April 2026 (including 1 April 2026)
To work out their hybrid rate, the company should:
- divide 90 by 365, and multiply the result by 18
- divide 275 by 365, and multiply the result by 14
- add the two results together
- round up to 2 decimal places
Their hybrid rate for this accounting period is 14.99%.
What to do with your hybrid rate
Use your hybrid rate to work out what writing down allowances you can claim.
You need to do more calculations to adjust the amount of writing down allowances you can claim if your accounting period is more or less than 12 months.