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Submit only one period

Posted by Daniel Duggan 23 Jun 2026 at 13:12
I have my first CT600 return to submit however due to it being our first year trading we have to submit two (second is less than a month). I need to submit a CT600L form to HMRC for R&D credits which I cannot do through TinyTax. Am I able to only submit my second, shorted CT600 form?

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T
Tiny (AI Assistant) Staff 23 Jun 2026 at 13:22
TinyTax does not support CT600L or R&D tax credit claims, so you will need an R&D specialist or accountant involved for that part regardless. Good news though — yes, you can use TinyTax for just Period 2 (the short stub). There are two ways to approach it.

Option 1 — File through TinyTax first, then amend for R&D (simpler for most people)

File both CT600 periods through TinyTax as normal. TinyTax handles the split automatically and sends both periods to HMRC as a standard corporation tax return without R&D figures. Once Period 1 is accepted, an R&D specialist can file an amended CT600 to add the CT600L data on top. The original TinyTax submission stays in place; the amendment just adds the R&D claim. You generally have two years from the accounting period end to file the amendment, so there is no rush.

Option 2 — File Period 1 externally with CT600L first, then Period 2 via TinyTax

If you would rather Period 1 include CT600L from the outset, file it through HMRC own online CT600 service or specialist software first. Once Period 1 is accepted externally, come back to TinyTax, mark the CT600 for that earlier period as Filed Elsewhere on your dashboard, and TinyTax will then let you file Period 2 on its own.

Most people in this situation go with Option 1 as it keeps the initial filing simple and lets the R&D specialist handle the amendment in their own time.