Hi,
Great questions. Many first-time directors find this confusing, so here's a full walkthrough.
1. Can I file the CT600 and Companies House accounts together?
They're two separate legal filings that go to two different bodies:
Company Tax Return (CT600): sent to HMRC. It includes the CT600 form, your full accounts and a tax computation, all in iXBRL format.
Annual accounts: sent to Companies House. These are your statutory accounts, often a shorter version for small and micro companies.
They're separate submissions, but you don't have to prepare them twice. With WeFile you enter your figures once. It then produces both sets of documents and sends the CT600 to HMRC and the accounts to Companies House from the same filing.
HMRC only accepts accounts and computations in iXBRL (tagged digital format), so a plain PDF won't work. WeFile creates the iXBRL for you.
2. What do I need before I start?
Have these ready:
Company registration number (CRN): 8 characters, on your Certificate of Incorporation.
Corporation Tax UTR: the 10-digit Unique Taxpayer Reference HMRC posts to your registered office after incorporation.
Companies House authentication code: a 6-character code posted to your registered office. It works like a signature for online filings. If you've lost it, you can request a new one from Companies House, but it arrives by post, so allow extra time.
Government Gateway user ID and password for your company's HMRC Corporation Tax account.
Your financial figures for the period:
Profit & loss: turnover, cost of sales, expenses, depreciation, and so on.
Balance sheet: fixed assets, stock, debtors, cash, creditors, share capital, reserves.
Prior-year figures (the comparatives), if this isn't your first year.
Tax-specific details: capital allowances on equipment or vans, any losses brought forward, any director's loans still owed at the year end (these may need form CT600A), and expenses that can't be deducted for tax, such as client entertaining.
If you use Xero, QuickBooks or FreeAgent, you can import your trial balance into WeFile instead of typing everything in. WeFile also checks that your P&L and balance sheet agree, so mistakes are caught before you submit.
3. What are the deadlines?
You've got them right. For a typical private limited company:
Corporation Tax payment: due 9 months and 1 day after the end of the accounting period.
Accounts to Companies House: due 9 months after the accounting reference date (your year end).
CT600 to HMRC: due 12 months after the end of the accounting period.
Watch out for:
First accounts after incorporation: these are due 21 months after the date of incorporation, not 9 months after the first year end.
You pay tax before the return is due. Many directors miss this because the payment deadline comes 3 months before the CT600 deadline.
Periods longer than 12 months: HMRC accounting periods can't be longer than 12 months. If your first accounts cover, say, 15 months, you need two CT600s (12 months + 3 months), even though Companies House gets one set of accounts. WeFile spots this and splits the return for you.
Late filing penalties:
HMRC: £100 the day after the deadline, another £100 at 3 months late, then tax-based penalties of 10% of the unpaid tax at 6 and 12 months. If you're late three times in a row, the fixed £100 penalties rise to £500 each.
Companies House: an automatic penalty that rises the longer the accounts are overdue, and doubles if you're late two years in a row. Check gov.uk for the current amounts.
4. My company didn't trade. Is there a simpler dormant route?
Yes. A company is usually dormant if it had no "significant accounting transactions" during the period. Paying the Companies House confirmation statement fee or buying shares on incorporation doesn't count as trading.
Companies House: you still have to file accounts every year, but dormant accounts are very short: basically a simple balance sheet with a few required statements.
HMRC: if HMRC has sent you a "notice to deliver a Company Tax Return", you must still file a CT600, even with nil figures. If HMRC has confirmed your company is dormant for Corporation Tax, you may not need to file until it starts trading.
WeFile has a dedicated dormant route that keeps the questions to a minimum: Dormant company accounts
5. How much Corporation Tax will I pay?
For accounting periods from 1 April 2023:
Profits up to £50,000: taxed at the 19% small profits rate.
Profits between £50,001 and £250,000: taxed at 25% minus marginal relief, so the effective rate is between 19% and 25%.
Profits over £250,000: taxed at the 25% main rate.
The £50k and £250k limits are reduced if your company has associated companies (they're divided by the number of associated companies plus one). They're also pro-rated for periods shorter than 12 months. WeFile applies all of this automatically. You can also estimate your bill first with the free tax calculator.
Common things to get right:
Depreciation isn't tax-deductible. It's added back, and you claim capital allowances instead. The Annual Investment Allowance gives 100% relief on most equipment.
Client entertaining must be added back as a disallowable expense.
Overdrawn director's loan account: if a director owes the company money at the year end and doesn't repay it within 9 months, the company may owe extra s455 tax via form CT600A. WeFile handles this within the same return.
Losses from previous years can reduce this year's taxable profit.
6. Which accounts format do I need?
For accounting periods starting on or after 6 April 2025, the size limits are:
Micro-entity (FRS 105): turnover up to £1m, balance sheet total up to £500k, up to 10 employees (you must meet at least 2 of the 3). This gives the simplest accounts.
Small company (FRS 102 Section 1A): turnover up to £15m, balance sheet total up to £7.5m, up to 50 employees.
Most one-person and small owner-managed companies qualify as micro-entities.
7. Are there video walkthroughs?
Yes. We've put together free step-by-step videos covering the whole process:
👉 WeFile video tutorials
A good order to watch them:
Getting Started: Dashboard Tour: adding your company and finding your way around.
CT600 & company accounts: every step of the filing wizard, from company details to submission.
Dormant, VAT and Self Assessment guides, if they apply to you.
Quick checklist before you submit
✅ The P&L and balance sheet agree, and closing reserves match.
✅ Prior-year comparatives match last year's filed accounts.
✅ Depreciation is added back and capital allowances are claimed.
✅ Director's loan balances at the year end are checked (CT600A if needed).
✅ The accounting period is 12 months or less for each CT600.
✅ The tax has been paid, or is scheduled, by the 9-months-and-1-day deadline.
✅ You have your authentication code and Government Gateway details.
Useful links: