Software-Only Filing: What Changed and What You Need

Both free government filing services have now closed. If you used to file on HMRC's or Companies House's own websites, you need commercial software for both filings from now on.

What Closed, and When

Service	Closed	What it means now
HMRC's free CT600 service (CATO)	31 March 2026	Corporation Tax returns must go through commercial software
Companies House WebFiling for accounts	31 March 2026	Accounts must be filed as iXBRL through commercial software

Both closures apply whatever your company's size or turnover. There is no small-company or micro-entity exemption from either.

Confirmation statements (CS01), director changes and address changes were not affected — those can still be filed on the Companies House website.

Are Small Companies Exempt From Filing With Software?

No. There is no exemption from software filing based on turnover, company size, micro-entity status or dormancy. A very small limited company that used to file on HMRC's own website has to use commercial software now, exactly like any other company.

Is There Any Exemption At All?

Not from the software requirement itself. There is one narrow route, and it is an exemption from filing online at all rather than from using software: HMRC can agree to accept a paper CT600 where online filing is not reasonably practicable for you, or on certain religious-society grounds.

That is HMRC's decision, not something you can elect. Ring the Corporation Tax helpline on 0300 200 3410 to ask. If HMRC agree, they issue the paper form themselves — the CT600 PDF you download from filing software is a review copy for checking your figures and cannot be posted in.

These agreements are given sparingly, so it is not something to plan around.

What You Need to Get Set Up

For the CT600

• Your company's Government Gateway credentials (User ID and password)
• Your Unique Taxpayer Reference (UTR) — the 10-digit number from HMRC
• Your company registration number
• Your accounts or a trial balance for the period

There is no separate "connect to HMRC" step for Corporation Tax — you enter your Gateway credentials at the point of submitting. That is HMRC's design and every CT600 product works the same way.

For the Accounts

• Your Companies House authentication code
• Your figures for the period, and the previous year's comparatives

What to Look For in Software

Essential

• HMRC-recognised for CT600
• Companies House accounts filing
• Automatic iXBRL tagging — this is the part HMRC and Companies House both insist on, and you should never have to do it by hand
• Validation before submission

Worth having

• Trial balance import from your bookkeeping software
• Tax calculated for you, including marginal relief
• Prior year comparatives fetched automatically
• Multiple company support if you file for more than one

Doing Both Filings in One Place

Your accounts are needed twice: Companies House require them, and HMRC require them attached to the Company Tax Return. Filing them at Companies House does not discharge the HMRC obligation.

Software that covers both means entering your figures once. TinyTax files the CT600 to HMRC and the accounts to Companies House from the same set of figures, and generates the iXBRL automatically.

What It Costs

TinyTax's pricing:

Plan	Price	Covers
Dormant	£20/year + VAT	One dormant company
Solo	£59/year + VAT	One trading company
Portfolio	from £99/year + VAT	Multiple companies, tiered by count

Other providers in this market typically run from £100 to £300 a year and upwards. Practice-grade software is built for accountants filing for many clients — if you are a director filing for your own company, you do not need it.

Common Mistakes

Assuming small companies were exempt

Neither closure carved out small, micro-entity or dormant companies. If you are still looking for the free route, it is not there.

Not downloading your HMRC filing history

Returns filed through CATO are no longer accessible now the service has closed. If you kept copies, hold on to them — HMRC can enquire into returns up to six years old.

Filing accounts at Companies House and stopping

HMRC still need the accounts with your Company Tax Return. Software that does both in one submission avoids this.

Choosing software built for accountants

If you file for one company, accountant-grade software is more than you need and priced accordingly.

What's Coming Next

Further Companies House changes take effect on 1 April 2028 — small companies and micro-entities will have to file a profit and loss account, abridged accounts are being withdrawn, and audit exemption statements are being strengthened. Nothing needs doing about those now.

Summary

• Both free government services closed on 31 March 2026
• Software is required for the CT600 and for the accounts, at any company size
• The only exemption is HMRC agreeing to a paper return, which they grant sparingly
• You need Gateway credentials and your UTR for HMRC, and your authentication code for Companies House
• Doing both filings in one place means entering your figures once

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TinyTax handles both the CT600 and your accounts. Get started →