HMRC CT600 Online vs Software: Which Is Better?
For years, limited company directors filing a CT600 had a choice: use HMRC's own free online service, or go with commercial filing software. That choice has now gone. HMRC's free online accounts and Company Tax Return service closed permanently on 31 March 2026 — the closure was announced jointly by HMRC and Companies House back in March 2025.
This guide compares the two routes honestly — what HMRC's service actually offered, where software does better, and what your options look like now that software is the only DIY filing route.
The Two Filing Routes Explained
HMRC's CT600 Online Service (Now Closed)
HMRC provided a free online service through the Government Gateway — formally the "online accounts and Company Tax Return service" — that let you file your Company Tax Return directly. It was designed for unrepresented small companies with straightforward tax affairs, and it ran for over a decade before closing on 31 March 2026.
What it offered:
- Free to use (no subscription or per-filing fees)
- Direct submission to HMRC
- Built-in templates that generated iXBRL accounts and computations from your keyed-in figures
- The option to file your annual accounts to Companies House at the same time
- Available 24/7 through the Government Gateway
Commercial Filing Software
Dedicated CT600 software — like TaxPipe — is built specifically to make corporation tax filing faster, easier, and less error-prone. These tools handle the CT600, iXBRL accounts, and HMRC submission in one workflow, submitted through your own Government Gateway account.
What it offers:
- Guided step-by-step filing process
- Automatic calculations (tax, marginal relief, capital allowances)
- iXBRL accounts generation built in for FRS 105 micro-entity and dormant companies; FRS 102 Section 1A small companies upload externally prepared iXBRL accounts
- Error checking before submission
- Support and help resources
Feature-by-Feature Comparison
Let's break down how the two routes compared while both existed — it's a useful lens for judging what to look for in software now.
1. Cost
| Option | Price |
|---|---|
| HMRC online (closed 31 March 2026) | Free |
| Commercial software | Typically £50–£200 per filing |
HMRC's service was free — that was its biggest selling point. But free didn't always mean cheap if it took you hours longer or its rigid templates didn't fit your company.
The real cost calculation: if a clunkier process takes you 3–4 extra hours and your time is worth even £20/hour, you've already spent more than most software costs. Factor in the risk of penalties from errors, and "free" could become expensive. TaxPipe, for example, charges a flat £59 per filing.
2. iXBRL Accounts
Since April 2011, all Company Tax Returns must include accounts in iXBRL format — a tagged, machine-readable version of your financial statements.
HMRC online: Contrary to a common misconception, the free service did generate iXBRL accounts and computations itself. You keyed your figures into its templates and it produced the tagged accounts for you — and could file them to Companies House too. You only needed separate iXBRL preparation if you chose to attach your own accounts instead of using the built-in templates.
Commercial software: Generates iXBRL accounts as part of the filing process for micro-entity (FRS 105) and dormant companies — you enter your figures and the software handles the tagging, formatting, and submission. FRS 102 Section 1A small companies upload externally prepared iXBRL accounts instead.
The real gap wasn't iXBRL — it was eligibility and flexibility. HMRC's service had strict eligibility criteria and rigid templates aimed at the simplest companies. If your circumstances fell outside them, you were pushed to software anyway. And since 31 March 2026, software is the route for everyone.
3. Ease of Use
HMRC online: The interface followed the CT600 form structure — box by box. If you knew exactly which boxes to fill in and what figures went where, it worked. But there was minimal guidance: you were expected to understand corporation tax terminology, know whether any supplementary pages applied, and work out several figures yourself.
Commercial software: Designed for people who aren't tax experts. Good software asks plain-English questions ("What was your turnover?", "Did you buy any equipment?") and fills in the correct CT600 boxes automatically. You don't need to know that turnover goes in Box 145 — the software handles the mapping.
4. Error Prevention
HMRC online: Basic validation only. It flagged a required box left empty or text entered where a number should be, but it didn't catch logical errors. For example:
- It wouldn't warn you if your expenses exceeded turnover in a way that suggested a mistake
- It wouldn't flag if you'd missed marginal relief you were entitled to
- It wouldn't sense-check your accounts figures against your CT600 for consistency
Commercial software: Built-in error checking catches problems before submission:
- Cross-checks between accounts and CT600 figures
- Alerts for common mistakes (wrong accounting period, missing reliefs)
- Validation against HMRC's submission rules
- Prompts for claims you might be entitled to
5. Marginal Relief and Tax Calculations
Since April 2023, the corporation tax rate depends on your profit level — 19% on profits up to £50,000, 25% on profits over £250,000, and a sliding scale in between. That sliding scale requires a marginal relief calculation, and the thresholds are divided between associated companies.
HMRC online: You had to work through the marginal relief position yourself for anything beyond the simplest cases. Get it wrong, and you'd overpay or underpay tax.
Commercial software: Calculates marginal relief automatically based on your profits and the number of associated companies. One less thing to get wrong.
6. Capital Allowances
If your company has purchased equipment, vehicles, or other qualifying assets, you need to calculate capital allowances — including the Annual Investment Allowance.
HMRC online: You calculated allowances manually and entered the figures. You needed to know the correct rates, pools, and qualifying criteria.
Commercial software: Walks you through asset purchases and calculates allowances automatically, handling AIA and writing-down allowances on the pools.
7. Record Keeping and History
HMRC online: Once submitted, you could view your return through HMRC's systems. But you didn't get a local copy of your working papers or an easy way to reference previous years when preparing the next return — a bigger problem now the service has closed and its templates are no longer accessible for new filings.
Commercial software: Stores your filing history. When you file next year, you can refer back to prior-year figures — opening balances, brought-forward losses, capital allowance pools — saving significant time.
8. Support
HMRC online: General HMRC helpline (long wait times). No specific support for using the filing tool. Help pages existed but tended to be generic.
Commercial software: Dedicated support teams who understand both the software and the tax rules. In-app guidance, help articles, and often live chat or email support.
When HMRC's Online Service Made Sense
To be fair, HMRC's service worked acceptably if:
- Your company was dormant and you were filing a nil return
- Your company met the service's eligibility criteria and its templates fitted your accounts
- You were comfortable with corporation tax terminology and the CT600 structure
- Cost was your absolute top priority and you valued your time at zero
None of that matters now — the service closed on 31 March 2026 and no new returns can be filed through it.
Why Software Is Now the DIY Route
Software is the practical choice when:
- You need to submit iXBRL accounts with your CT600 (required for virtually every active company — software generates them automatically for FRS 105 micro-entities and dormant companies, or lets you upload externally prepared accounts if your company uses FRS 102 Section 1A)
- You're not a tax expert and want guided filing
- You want automatic calculations for marginal relief, capital allowances, and tax due
- You're filing for a trading company with real income and expenses
- You want error checking before submission
- You plan to file yourself going forward and want your filing history in one place
For the vast majority of small limited company directors filing without an accountant, software is now the only realistic DIY option — the alternative is paying an accountant.
Cost Comparison: The Full Picture
With the free HMRC route gone, here's what the realistic options look like for a typical small company filing:
| Approach | Direct cost | Time cost (est.) | Risk cost | Total effective cost |
|---|---|---|---|---|
| Dedicated filing software | £50–£200 | 2–4 hours | Lower error risk | £90–£280 |
| Accountant | £500–£1,500 | Minimal | Lowest risk | £500–£1,500 |
Dedicated filing software hits the sweet spot — significantly cheaper than an accountant, with guided workflows and automatic calculations doing most of the heavy lifting.
HMRC's Free Filing Service Has Ended
HMRC and Companies House announced in March 2025 that the free online accounts and Company Tax Return service would close, and it shut permanently on 31 March 2026. Roughly 1.5 million UK companies were affected.
What that means in practice:
- Company Tax Returns (CT600) must now be filed using commercial software
- Companies House accounts must be filed separately — through Companies House's own online services or accounts software — because the joint "file once to both" feature died with the service
- Returns previously filed through the HMRC service remain on record, but you can't start new ones there
Making the Switch to Software
If you previously used HMRC's service (or have been dreading your first DIY filing), getting set up with software is straightforward:
- Gather your documents — use our CT600 filing checklist
- Choose your software — compare options
- Enter your figures — follow the guided process
- Review and submit — the software files to HMRC through your own Government Gateway account
With TaxPipe, the process takes most small company directors 2–3 hours from start to submission. No tax knowledge required — just your accounts figures and your Government Gateway login.
Frequently Asked Questions
Can I still file my CT600 for free?
No — HMRC's free online filing service closed on 31 March 2026, and there is no longer a free end-to-end route for active companies. Commercial software is now required. See our guide to low-cost CT600 filing options.
Has HMRC's online CT600 service been discontinued?
Yes. HMRC and Companies House announced the closure in March 2025, and the service shut permanently on 31 March 2026. All companies must now file their CT600 using commercial software.
Do I need iXBRL accounts to file a CT600?
Yes — companies must submit accounts in iXBRL format with their CT600. Dormant companies filing nil returns are a simpler case, but the return must still be filed correctly. Read more about iXBRL requirements.
What's the cheapest way to file my CT600 now?
Dedicated filing software that handles both the CT600 and iXBRL accounts typically offers the best value — far cheaper than an accountant. See our cheapest filing options guide.
I used HMRC's free service last year — what do I do now?
Start fresh in your chosen software. Your previous returns stay on record with HMRC, but nothing transfers automatically — have last year's return and accounts to hand for figures like brought-forward losses and capital allowance pools.
How long does it take to file a CT600 with software?
Most users report 2–4 hours with dedicated software. Users of HMRC's old service often reported 6–10 hours, largely because of its minimal guidance and manual calculations.
The Bottom Line
While it existed, HMRC's CT600 online service was genuinely free and did more than people often gave it credit for — including generating iXBRL accounts from your keyed-in figures. But it offered minimal guidance, no automatic tax calculations, and rigid eligibility rules — and it closed permanently on 31 March 2026.
That leaves two realistic routes: an accountant, or dedicated filing software. Software costs a fraction of an accountant's fees while doing most of the heavy lifting for you. For the majority of small company directors, it's the practical sweet spot between fully DIY and fully outsourced.
Ready to file? Start your CT600 filing with TaxPipe — guided, automatic, and submitted directly to HMRC for a flat £59.