Filing a Late CT600
Yes, you can file a late CT600 with TinyTax. Here's what penalties apply and how to submit.
Can you still file your CT600 after the deadline? Yes — TinyTax lets you file late returns. This guide covers what to expect, what penalties apply, and how to file.
Can I File Late?
Yes. TinyTax does not block late filings. If your filing deadline has passed, your dashboard will show the filing in red to indicate it's overdue, but the submit button remains active. You can file at any time.
HMRC Late Filing Penalties
Penalties are automatic and cumulative:
| How late | Penalty |
|---|---|
| 1 day | £100 |
| 3 months | Another £100 (total £200) |
| 6 months | HMRC estimates your tax and charges 10% of the unpaid amount |
| 12 months | Another 10% of the unpaid amount |
- Penalties apply even if your company owes £0 in tax (e.g., dormant companies)
- If your company filed late in either of the previous two years, the £100 penalties double to £200 each
- HMRC also charges late payment interest on any overdue tax (the rate changes periodically)
Filing Deadlines
| Filing | Deadline |
|---|---|
| CT600 (corporation tax return) | 12 months after your accounting period end |
| Corporation tax payment | 9 months and 1 day after your accounting period end |
| Companies House accounts | 9 months after your accounting period end (6 months for public companies) |
How to File a Late CT600
The process is the same as filing on time:
- Log in to TinyTax and go to your dashboard
- Select the overdue filing (shown in red)
- Complete the CT600 form as normal
- Submit to HMRC
How Far Back Can I File?
TinyTax supports filings for accounting periods ending on or after 1 April 2022. This is determined by the HMRC taxonomy requirements — periods before this date use an older format that TinyTax doesn't support.
If you need to file for a period ending before April 2022, you'll need to use HMRC's own filing service or other CT600 software.
Can I Appeal a Penalty?
HMRC may accept a reasonable excuse for late filing. Common reasonable excuses include:
- Serious illness
- Death of a partner or close relative
- Unexpected hospital stay
- HMRC service outage
- Fire, flood, or other disaster affecting records
To appeal, use HMRC's online service or write to HMRC explaining the circumstances.
Common Questions
Q: My company is dormant — do I still get penalised for filing late? A: Yes. HMRC charges the flat penalties (£100, then £200) regardless of whether you owe tax. The 10% penalties at 6 and 12 months are based on unpaid tax, so they'd be £0 for a dormant company — but the flat penalties still apply.
Q: I didn't know I had to file — is that a reasonable excuse? A: Unfortunately, no. HMRC expects all company directors to know their filing obligations. However, if HMRC never issued a Notice to Deliver, you may have grounds for appeal.
Q: Will HMRC know I filed late? A: Yes. HMRC records the submission date and applies penalties automatically. Filing through TinyTax doesn't change this — the penalty is based on when HMRC receives the return relative to the deadline.
Q: Can I file for multiple late years at once? A: Yes. TinyTax lets you file for each accounting period individually. Select each overdue period from your dashboard and file them one at a time.
Q: I submitted late but haven't received a penalty notice yet — what should I do? A: HMRC sometimes takes weeks or months to issue penalty notices. Don't assume no notice means no penalty. If you've filed late, expect a penalty letter.
Still Have Questions?
If you're worried about late filing or need help with an overdue return, get in touch.
Last updated: February 2026
Was this guide helpful?
Thanks for your feedback!