Mathematical checks
Do your figures balance? Does the P&L reconcile with the balance sheet?
PRODUCT TOUR · Updated 16 February 2026
How it works: file your company tax in 5 steps.
SimpleCompanyTax takes you from company lookup to HMRC-ready CT600 and iXBRL accounts in a single guided session. Most directors complete the entire process in under 30 minutes — no jargon, no spreadsheets, no Government Gateway gymnastics.
- No card required to preview
- CT600 v3 schema compliant
- Under 30 minutes for most filings
CHECKLIST
Before you start: what you'll need.
Have these ready before you begin. Don't worry if you're unsure about some figures — the wizard explains each field as you go.
- Your company number — the 8-digit number from Companies House (e.g. 12345678).
- Your company authentication code — the 6-character code from Companies House, used to authorise filings.
- Your basic financial figures — turnover, expenses, and any other income for the accounting period.
- Your accounting period dates — the start and end dates of the period you're filing for.
01 — CONNECT
Connect your company.
Enter your company number and we fetch your details from Companies House instantly:
- Company name and registered address
- Date of incorporation
- Current directors
- Accounting reference date
- Filing history
You'll also enter your Companies House authentication code, which is stored securely and used when you're ready to submit.
About 2 minutes
Screenshot: /onboarding company lookup card
02 — INPUT
Enter your financial data.
Our guided wizard walks you through the information needed for your CT600 return and statutory accounts. The form is broken into clear sections:
Company profile and period
Confirm your accounting period dates and select your company type (trading, dormant, or property income).
Tax-scope inputs
- Turnover (total sales / revenue)
- Cost of sales
- Operating expenses (rent, utilities, salaries)
- Other income (bank interest, investment income)
- Depreciation and capital allowances
- Directors' remuneration
Accounts data
- Balance sheet figures (fixed assets, current assets, creditors, share capital)
- Profit & loss confirmation
Each field includes a plain-English explanation. If a field doesn't apply to your company, you can leave it as zero.
10–20 minutes depending on complexity
Screenshot: wizard tax-scope inputs
03 — VALIDATE
Validate automatically.
Once you've entered your figures, our system runs four automatic validation checks:
CT600 compliance
Every required CT600 box populated correctly against HMRC schema v3.
Tax calculation
Corporation tax computed across all applicable bands, including marginal relief.
iXBRL tagging
Accounts tagged against the correct FRS 105 taxonomy.
If any issues are found, you'll see clear error messages explaining what needs to be corrected.
Automatic (a few seconds)
04 — REVIEW
Review everything before filing.
Before filing, you can review and download everything that will be submitted:
- CT600 return (XML with all computed values)
- iXBRL statutory accounts (HMRC + Companies House tagged)
- Tax computation (step-by-step breakdown)
Review the summary to make sure everything looks correct. You can go back and edit any figures if needed — regenerating documents is unlimited and included in your subscription.
5 minutes
Screenshot: /review page
05 — FILE
Submit to HMRC — and keep the receipt.
When you're satisfied with your documents, you're ready to submit:
- CT600 XML submitted to HMRC via their Government Gateway
- iXBRL accounts accompanying the CT600 submission
- IRmark receipt stored on your account
- Downloadable copies of all documents for your records
About 1 minute
What happens after filing?
- HMRC processing — HMRC typically processes CT600 returns within a few days. You'll see the filing reflected in your HMRC online account.
- Companies House — Your iXBRL accounts can be filed separately at Companies House if needed.
- Payment — Remember to pay your corporation tax by the deadline (9 months and 1 day after your accounting period end). We calculate the liability — you arrange payment to HMRC.
FAQ
Frequently asked questions about the process.
How long does the whole process take?
Most micro-entity directors complete everything in 15–30 minutes. Dormant companies are even faster — often under 10 minutes.
Can I save my progress and come back later?
Yes. Your data is saved automatically as you go. You can close the browser and return at any time.
What if I make a mistake?
You can regenerate your documents as many times as you need — it's included in the subscription. Before final submission, nothing is sent to HMRC.
Can I download the documents?
Yes. CT600 XML, iXBRL accounts, and the tax computation are all downloadable from your account at any time.
Ready to file in 30 minutes?
From £10 per company, per year. One flow for HMRC and Companies House — £10 dormant, £25 micro-entity.