CT600 Box 3 (Tax Reference) Blank in Draft Documents | TinyTax Support

CT600 Box 3 (Tax Reference) Blank in Draft Documents

If you download your CT600 draft and see Box 3 (Tax Reference) or the Tax Computation item 3 is blank, this is expected — the UTR is optional when downloading the draft. You enter it when you actually submit.

Why Is Box 3 Blank?

When you click Download CT600 on the preview page, a modal appears with two options:

  • Download PDF — downloads the form with Box 3 blank (quick option for draft review)
  • Add UTR to Box 3 — expands a section where you can enter your 10-digit UTR to include it in the PDF
The draft PDF is for your records only. TinyTax submits your CT600 digitally to HMRC, and your UTR is captured at the point of submission — not when you download the draft.

The same applies to your Corporation Tax Computation — if the UTR was not entered before generating the draft, item 3 (Tax Reference) will also appear blank in the draft document.

Will HMRC Reject My Submission Because of This?

No. TinyTax will not allow submission without a valid UTR. When you click Submit to HMRC on the preview page, a form appears asking for:

  1. Company UTR — your 10-digit tax reference (required)
  2. Government Gateway User ID — your 12-digit Gateway login ID
  3. Password
If the UTR is missing or invalid, TinyTax will reject the submission before it ever reaches HMRC. You cannot accidentally submit without one.

How to Find Your Company UTR

Your company UTR is a 10-digit number. Find it:

  • On HMRC letters addressed to your company (usually labelled "Unique Taxpayer Reference" or "UTR")
  • In your HMRC online Business Tax Account, under "Corporation Tax"
  • On the original Corporation Tax registration letter HMRC sent when your company first enrolled
⚠ Your company UTR is different from your personal Self Assessment UTR, and different from your Government Gateway login credentials. Make sure you use the company UTR, not your personal one.

How to Add the UTR to Your Draft PDF

If you want Box 3 filled in your draft documents:

  1. Go to the preview page for your filing
  2. Click Download CT600
  3. In the modal, click Add UTR to Box 3 to expand the input
  4. Enter your 10-digit company UTR
  5. Click Add UTR & Download PDF
This re-downloads the PDF with Box 3 populated. It does not affect your actual HMRC submission.

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