Capital Allowances for Company Cars on a CT600

TinyTax can file CT600 returns for companies that own a car, including electric and low-emission vehicles. This guide explains how to enter capital allowances for a company car in the Tax Computation section.

Why Cars Are Different

Cars cannot use the Annual Investment Allowance (AIA). Instead, HMRC requires cars to go into capital allowance pools, where a percentage is claimed each year as a Writing Down Allowance (WDA) — or, for qualifying vehicles, a First Year Allowance (FYA) in the year of purchase.

The applicable rate depends on the car's CO2 emissions:

How to Enter Car Capital Allowances in TinyTax

You calculate the allowable capital allowance figure yourself (based on the car's CO2 emissions and tax written-down value), then enter it in the Tax Computation section.

1. Open your filing and scroll to the Tax Computation section
2. Enter your capital allowance amount in the Annual Investment Allowance field
3. TinyTax deducts this from your taxable profit and includes it in your CT600 computation

Example

Your company purchased an electric car (0g/km) for £30,000 in May 2025 (after the FYA deadline). The car goes into the main pool. Year 1 WDA at 18% = £5,400. Enter £5,400 in the Annual Investment Allowance field.

What TinyTax Does Not Calculate Automatically

TinyTax does not maintain a running capital allowance pool or automatically calculate WDA percentages. You need to:

• Track the tax written-down value of the car each year
• Calculate the WDA (or FYA) for the period yourself
• Enter the figure in TinyTax

Common Questions

Can I use TinyTax if my company has a company car?

Yes. Enter the capital allowance amount in the Tax Computation section. TinyTax is a full CT600 filing solution for companies with company cars.

Does the car need to be declared anywhere else in the return?

The capital allowance appears in your Tax Computations document. For the CT600 itself, the deduction flows through to your taxable profit figure. If the car is a benefit in kind for a director or employee, that is a payroll (P11D) matter separate from the CT600 — TinyTax does not handle P11D filings.

Why does HMRC say I need commercial software?

HMRC's own free Corporation Tax filing service closed on 31 March 2026. All companies now need to use commercial software like TinyTax to submit CT600 returns electronically. This applies to all companies — not specifically those with company cars.