R&D Tax Credits and TinyTax — What We File and What We Don't

TinyTax files CT600 corporation tax returns and micro-entity statutory accounts to HMRC and Companies House. This guide explains what's included in a TinyTax submission and why R&D tax credit claims are outside our scope.

What TinyTax Submits to HMRC

Every TinyTax submission includes:

• CT600 return — the main corporation tax form with your trading figures, tax calculation, and any loss carry-forwards
• iXBRL statutory accounts — your profit & loss account and balance sheet in HMRC's required format
• Tax computations — showing how your taxable profit and tax liability were calculated

The iXBRL accounts generated by @AdamsWinter are correctly tagged to the HMRC schema. Financial figures including turnover, costs, gross profit, and net profit/loss are all included and tagged.

R&D Tax Credits Are Not Supported

@AdamsWinter does not currently support Research & Development (R&D) tax credit claims. This means the CT600 we file does not include:

• R&D enhanced expenditure (Boxes 530–535 on the CT600)
• SME R&D relief calculations
• Research and Development Expenditure Credit (RDEC)
• The CT600L supplementary pages

If HMRC's R&D team queries your submission and says the accounts contain "no financial figures" or "no R&D data", this is because the R&D boxes are absent from the return — not because the statutory accounts are malformed or blank. The underlying accounts and CT600 figures are correct.

How to Claim R&D Tax Credits

To claim R&D tax credits, you'll need to file an amended CT600 that includes the R&D supplementary pages. Since the original return was already accepted by HMRC, the amendment adds the R&D data on top — you do not need to cancel or refile the original return.

The most practical routes are:

1. R&D tax specialist or accountant — they can prepare and file the amendment, including the CT600L pages and enhanced expenditure calculations
2. HMRC's own CT600 online service — includes the R&D supplementary pages
3. Commercial CT600 software that supports R&D claims (e.g. Taxfiler, Andica)

Amendment Deadline

You generally have two years from the end of the accounting period to file an amended return. For example, for a period ending 30 November 2025, the amendment deadline is 30 November 2027.

Confirming Your Submission Details

If HMRC or an R&D adviser asks for evidence that your original CT600 was filed correctly, you can provide:

• The transaction ID from your @AdamsWinter dashboard (shown on the submission confirmation page)
• The acceptance timestamp — HMRC accepts returns within seconds via the Government Gateway
• The iXBRL accounts file — downloadable from your @AdamsWinter dashboard

Common Questions

"HMRC said the accounts contain no financial figures — are they correct?"

Yes. The accounts @AdamsWinter filed contain all the financial figures from your P&L and balance sheet, correctly tagged in iXBRL format. When HMRC's R&D team describes the accounts as having "no figures", they mean the R&D-specific boxes (530–535) are empty — which they are, because @AdamsWinter does not file R&D supplementary pages.

"Do I need to refile my original return before claiming R&D?"

No. Your accepted CT600 remains valid. You file an amendment alongside it — the amendment adds the R&D data without replacing the original.

"Will claiming R&D change my corporation tax liability?"

Yes — R&D relief typically reduces your corporation tax liability or generates a payable credit. Your R&D adviser will calculate the adjusted figures as part of the amendment.