Yes, you can file your own company accounts. There is no legal requirement to use an accountant, and Companies House does not charge a penny to accept them.
But the answer changed on 31 March 2026, and most guidance has not caught up. Filing at Companies House is still free and still straightforward. Filing the tax side with HMRC is no longer free at all — the free government service closed, and a Company Tax Return now goes through commercial software.
That asymmetry is the whole decision.
The two filings, and why only one is still free
Every trading limited company files twice from the same underlying accounts.
| Companies House | HMRC | |
|---|---|---|
| What you file | Accounts (a micro-entity files the balance sheet only) | Full accounts plus a CT600 and a Corporation Tax computation |
| Free government route | Yes — online, software or paper | No — closed 31 March 2026 |
| Software required | Not until April 2028 | Yes, since 1 April 2026 |
| Format | Online via WebFiling, or iXBRL via software | iXBRL only |
| Deadline | 9 months after the accounting reference period ends | 12 months after the accounting period ends |
| Paper route | Available, by post | Only with a reasonable excuse, or filing in Welsh |
HMRC’s free filing service closed on 31 March 2026. The joint “File your accounts and Company Tax Return” service that let small companies submit both sides free of charge is gone. From 1 April 2026, HMRC directs companies to commercial software.
Companies House filing remains free. Web filing still works, and will until April 2028.
So the realistic DIY position: the Companies House half costs nothing, the HMRC half now costs whatever your software charges. Budget CT600 packages exist, but “free DIY” as a complete route no longer exists for a trading company.
Filing at Companies House yourself
The mechanics are genuinely simple.
What you need:
- your company number
- a Companies House account and your company authentication code — a 6-character code posted to your registered office
- accounts approved by the board and signed by a director, with the signatory’s name printed on the balance sheet
- for a micro-entity, the statement above the signature confirming the micro-entity provisions were used
How to file: use the Companies House online accounts service, or your accounting software if it supports Companies House submission. Paper accounts can still be posted to Companies House main office, Crown Way, Cardiff CF14 3UZ — but post is slow, and the deadline is the date of receipt, not the date of posting.
What gets rejected. Companies House cannot accept accounts that fail Companies Act requirements. The recurring causes: an unsigned balance sheet, a missing director’s name, the missing micro-entity statement, the wrong accounting period, or a format that does not match the company’s size. A rejection does not pause the clock — resubmit after the deadline and the penalty applies.
Filing the CT600 yourself
This is the harder half, and not only because of the software.
What you need:
- HMRC online services access, with your company’s Corporation Tax UTR and reference
- commercial software that can produce a CT600, a Corporation Tax computation and the accounts, all tagged in iXBRL — a machine-readable format that labels each figure so HMRC’s systems can read it
- the tax computation itself: accounting profit adjusted for disallowable expenditure, capital allowances, and anything else that differs between accounting rules and tax rules
The computation is the work, not the form. Filling in the CT600 is data entry. Getting to the right taxable profit takes judgement, and it is where self-filed returns most often go wrong.
The payment comes before the return. Corporation Tax is due 9 months and 1 day after the accounting period ends, but the CT600 is not due for 12 months. You calculate the liability roughly three months before you are required to declare it.
Where DIY genuinely works
- Dormant companies. No trade, no transactions, a simplified dormant accounts format. The clearest case for filing yourself.
- Single-director companies with almost no activity — one bank account, a handful of invoices, no assets, salary and dividends only.
- Directors with a finance background who already understand disallowable expenditure and capital allowances.
- Companies where the numbers are small enough that a mistake is cheap. At £8,000 of taxable profit, the cost of getting it slightly wrong is bounded.
Where DIY usually fails
A director’s loan account. Money moving between you and the company is the most common source of error. Overdrawn balances can trigger a s455 charge, and the treatment is not obvious.
Capital allowances. Deciding what qualifies, and whether to claim full expensing, the annual investment allowance or writing-down allowances, is a judgement with a real cash consequence.
Mixed personal and business spending. Home office, vehicle, phone, subsistence. Each has its own rule, and most self-filers apply a rough percentage that would not survive an enquiry.
Anything structural. Multiple share classes, corporate shareholders, property, multi-currency trading, groups, or a year straddling a change of accounting date.
R&D claims. These carry their own compliance regime and additional information requirements. Do not attempt one from a general software package without advice.
Crossing a size threshold. A company that stops qualifying as a micro-entity moves to FRS 102 Section 1A, restates comparatives and produces a materially different set of accounts.
A backlog. Two or three overdue years is not three times the work of one. Penalties are already running at both Companies House and HMRC, and the sequencing matters.
The costs nobody prices in
Rejection risk. A rejected filing that pushes you past the deadline costs £150 minimum at Companies House, doubling to £300 if you also filed late the previous year. That is often more than the difference between DIY and a fixed fee.
Your time. A first-time self-filer typically loses a weekend to it, more if the software rejects the iXBRL tagging.
Liability. File it yourself and every error is yours. Directors are personally responsible for delivering accounts on time, and failing to file is a criminal offence, not just a penalty matter. An ICAEW-regulated firm carries professional indemnity insurance and answers to a regulator.
No second pair of eyes. Most of what an accountant catches is not the return but the thing you did not know to ask about.
What changes in April 2028
From April 2028, Companies House web filing and paper submission close for accounts. All accounts must be filed using commercial software in iXBRL format, though both routes stay open for confirmation statements and other filings.
At the same point, micro-entities and small companies must file a profit and loss account alongside the balance sheet, abridged accounts are abolished, and a publication opt-out lets small and micro companies keep the P&L off the public register while Companies House, HMRC and law enforcement retain access.
The date was originally announced as April 2027 and confirmed as April 2028 on 9 June 2026. Plenty of published guidance still shows the older date.
The practical effect for DIY filers: after April 2028, both halves need commercial software. The free Companies House route disappears.
Frequently asked questions
Is it legal to file my own company accounts?
Yes. There is no requirement to use an accountant. Directors are personally responsible for delivering accounts on time and in the correct format, whoever prepares them.
Can I still file company accounts for free?
At Companies House, yes — filing accounts is free online, by software and on paper. With HMRC, no. The free government service closed on 31 March 2026, and a Company Tax Return now requires commercial software unless you have a reasonable excuse to file on paper or are filing in Welsh.
Do I need an accountant for a dormant company?
Usually not. Dormant accounts use a simplified format and are the clearest case for filing yourself. You still need to file every year, and the late filing penalty applies to dormant companies exactly as it does to trading ones.
What is iXBRL and do I need it?
iXBRL is a machine-readable format that tags each figure in your accounts so HMRC’s systems can read them. It is mandatory for the HMRC filing. It is not required for Companies House web filing until April 2028.
What happens if my company accounts are rejected?
Companies House returns them for correction and the deadline does not move. If the corrected accounts arrive after the deadline, the automatic late filing penalty applies, starting at £150.
When DIY stops making sense
The test is not whether you can file your own accounts. Most directors can. It is whether the time, the software cost and the risk of a rejected filing add up to less than a fixed fee — and whether you would spot the thing you did not know to look for.
SmartFiling prepares and files micro-entity accounts from £299, covering FRS 105 accounts, the CT600, iXBRL tagging and submission to both Companies House and HMRC. One fixed price agreed upfront, seven working day turnaround, and every filing reviewed and signed off by an ICAEW Chartered Accountant.
