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.

⚠ File as soon as possible to minimise penalties. HMRC charges penalties from day one — there is no grace period.

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

Important notes:

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)

ℹ The payment deadline is earlier than the filing deadline. Even if you haven't filed yet, pay any estimated tax by the 9-month mark to avoid late payment interest.

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

TinyTax handles the submission — HMRC accepts late returns through the same process as on-time returns.

I Can't See My Overdue Period on the Dashboard

If the period you need to file is older than the ones shown on your main Dashboard grid, it's still available — you just need to open the company detail drawer to reach it.

The main Dashboard grid shows the periods Companies House currently flags as due or recently due. Older periods (typically more than 1–2 years overdue) don't appear on the grid but are still in your company's filing history.

To access them:

On the Dashboard, click your company row (not the Start Filing button — click the row itself)
A detail drawer slides in from the right showing every period from your company's history
Each older period has its own Start Filing button
Click it and the CT600 form opens the same way as for recent periods

ℹ Earliest period first. If you're catching up on several years, file the earliest open CT600 first and work forwards — each year's losses and balances feed into the next.

If a period is entirely missing from the drawer as well (not just the grid), reply to support with the company number and the period end date, and we can check whether Companies House holds history for it.

How Far Back Can I File?

CT600 (corporation tax return): TinyTax supports CT600 filings for accounting periods ending within roughly the last 8 years. HMRC itself accepts late CT600 returns for any period — there's no deadline beyond which they'll refuse one — so late filings from years ago are still possible through TinyTax.

Companies House accounts: These require the CT2023+ taxonomy and are only supported for periods ending on or after 1 April 2022. If your accounts period is older, you'll need to file those through another route (most very old accounts periods have already been filed at Companies House anyway).

If you need to file a CT600 for a period older than 8 years, contact support and we'll see what we can do.

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

Not usually accepted: Being too busy, finding tax complicated, relying on someone else who let you down, or not knowing about the deadline.

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

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