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CT600 Capital allowances

I have submitted my CT600 but have noticed a few things:

1. How can we add our Tax Reference ID to the form (it asks for it when you submit, but it is not the PDF)

2. How can we tick that we qualify for SME exemption (Box 75) and box 45 for claim for earlier period

3. How do you enter the AIA (box 690) and other capital allowances?

Thanks

3 Comments

T
Tim Fouracre Staff 18 Jan 2026 at 18:31
Thanks for your questions. Let me address each one:

1. Tax Reference (UTR) on the PDF

The CT600 PDF is for your records only - it's not part of the digital filing to HMRC. The actual submission is sent electronically in XML format, which always includes your UTR.

If you'd like the UTR to appear on your PDF copy: when you click to download the CT600 PDF, you'll see a modal with the option to "Add UTR to Box 3". Click that toggle, enter your 10-digit company UTR, and download - it will then appear in Box 3 on the PDF.

2. Box 75 (SME exemption) and Box 45 (earlier period claim)

These boxes are not currently supported in TinyTax, again because the CT600 pdf is not part of the digital submission to HMRC.

- Box 45 is for claiming relief using losses carried back to an earlier period. If you need to carry back losses, you would need to make a separate claim to HMRC.

3. Annual Investment Allowance (AIA) and Capital Allowances

To enter your AIA:

1. Go to the Tax Computation section (below the Balance Sheet)

2. Click "Show all" next to the section header to reveal all fields

3. Look for "Less: Annual Investment Allowance" (Box 735)

4. Enter your capital allowance claim (capped at £1 million)

This reduces your taxable profit by the amount claimed.

Note: TinyTax currently supports the Annual Investment Allowance (Box 735) for straightforward equipment and machinery purchases. Other capital allowance types (writing down allowance, balancing charges, etc.) that would go in different boxes are not yet supported.

Please let me know if you have any other questions.
D
Debbie Wanstall 18 Jan 2026 at 19:02
Thanks Tim for your quick response. Overall I am happy with how easy the software is to use. Will you be adding in Balancing charges etc over the next year?
T
Tim Fouracre Staff 18 Jan 2026 at 20:51
We are planning to launch an "Advanced" company type in addition to trading/property/dormant which will have all the boxes that our users have been asking for, so yes, very likely.