CT600 Checklist: Everything You Need Before Filing
Filing a CT600 is much easier when you're prepared. This checklist covers everything you need to gather before starting your corporation tax return.
Essential Documents Checklist
Company Information
- Company registration number (8 digits)
- Unique Taxpayer Reference (UTR) - 10 digits
- Government Gateway login credentials
- Registered office address
- Accounting period dates (start and end)
Financial Records
- Trial balance or profit & loss summary
- Bank statements for the full period
- Sales invoices and records
- Purchase invoices and receipts
- Payroll records (if applicable)
Previous Filings
- Last year's CT600 (if not first year)
- Prior year accounts
- Brought forward losses (if any)
- Capital allowances pool values
Income Checklist
Trading Income
- Total sales/turnover
- Other trading income
- Commission received
- Service income
Non-Trading Income
- Bank interest received
- Investment income
- Rental income (if property held)
- Dividends received (note: not taxable for most companies)
- Capital gains (from asset sales)
Expenses Checklist
Staff Costs
- Gross salaries and wages
- Director's salary
- Employer's National Insurance
- Pension contributions (employer's)
- Benefits in kind costs
Premises Costs
- Rent
- Business rates
- Utilities (gas, electric, water)
- Insurance (property)
- Repairs and maintenance
Administrative Costs
- Accountancy fees
- Legal fees
- Bank charges
- Software subscriptions
- Office supplies
Operating Costs
- Travel and subsistence
- Vehicle expenses
- Phone and internet
- Marketing and advertising
- Professional subscriptions
Capital Expenditure Checklist
Fixed Assets Purchased
- Computer equipment
- Office furniture
- Machinery
- Vehicles (note CO2 emissions for cars)
- Tools and equipment
Information Needed per Asset
- Purchase date
- Purchase price
- Description
- CO2 emissions (cars only)
- Whether it's new or second-hand
Assets Sold or Disposed
- Date of disposal
- Sale proceeds
- Original cost
- Accumulated allowances claimed
Special Items Checklist
Disallowable Expenses
Identify and separate these (they're added back for tax):
- Client entertainment
- Personal expenses put through company
- Depreciation (replaced by capital allowances)
- Fines and penalties
- Non-business travel
Adjustments
- Private use adjustments
- Related party transactions
- Loans to directors (S455 implications)
Filing Requirements Checklist
For HMRC
- Completed CT600 form
- iXBRL accounts (attached to CT600)
- Tax computations
- Supplementary pages (if applicable)
For Companies House
- Balance sheet
- Notes to accounts
- Directors' report (if required)
Pre-Submission Checks
Accuracy Checks
- All income included?
- All allowable expenses claimed?
- Capital allowances calculated?
- Brought forward figures correct?
- Period dates accurate?
Balance Sheet Checks
- Assets = Liabilities + Equity?
- Opening balances match prior year closing?
- Director's loan correctly shown?
- Cash matches bank statements?
Compliance Checks
- Filing within deadline?
- Payment scheduled before deadline?
- Associated company details correct?
- Agent authorisation in place (if using one)?
By Company Type
Micro-Entity Checklist Additions
- Confirm you meet micro-entity criteria
- Two of three: turnover <£1m, assets <£500k, employees ≤10
First Year Filing Additions
- Period start date (incorporation date)
- Check if period exceeds 12 months (requires split)
- No prior year figures to enter
Dormant Company Checklist
- Confirm no trading activity
- No income received
- No expenses (or minimal bank charges only)
- Balance sheet position unchanged
Common Mistakes to Avoid
Data Gathering Mistakes
| Mistake | Prevention |
|---|---|
| Missing bank accounts | List all accounts at start |
| Forgetting petty cash | Include cash transactions |
| Wrong period dates | Double-check against Companies House |
| Missing invoices | Reconcile to bank statements |
Expense Mistakes
| Mistake | Prevention |
|---|---|
| Claiming entertainment | Separate clearly from other expenses |
| Including depreciation | Remove from expenses, claim capital allowances instead |
| Missing small purchases | Review bank statements thoroughly |
Income Mistakes
| Mistake | Prevention |
|---|---|
| Excluding bank interest | Check all bank statements |
| Wrong treatment of grants | Verify if capital or revenue |
| Missing sales invoices | Reconcile to accounting records |
Filing Timeline Checklist
3 Months Before Deadline
- Gather all documents
- Reconcile bank accounts
- Check for missing records
1 Month Before Deadline
- Complete trial balance
- Calculate capital allowances
- Draft CT600
2 Weeks Before Deadline
- Review and check all figures
- Prepare payment
- Have a second pair of eyes review (if possible)
Filing Day
- Final review
- Submit CT600 to HMRC
- File accounts to Companies House
- Schedule tax payment
- Save confirmation receipts
Frequently Asked Questions
What if I'm missing a document?
Request duplicates from your bank, suppliers, or HMRC. Keep notes of what you've done to reconstruct records.
How far back should records go?
Keep records for at least 6 years after the end of the accounting period they relate to.
Do I need original receipts?
Digital copies are acceptable. Bank statements can support expenses if receipts are lost.
What if my records are incomplete?
Use your best estimate based on available evidence. Note any estimates in your records. Consider professional help.
Printable Checklist Summary
Company Information:
- Company number
- UTR number
- Government Gateway login
- Bank statements
- Invoices (sales and purchases)
- Payroll records
- Trading income
- Interest and investments
- Other income sources
- Staff costs
- Premises costs
- Operating expenses
- Disallowable items identified
- Assets purchased
- Assets disposed
- Pool values brought forward
- Previous CT600
- Losses brought forward
- Capital allowances brought forward
- All figures verified
- Balance sheet balances
- Deadline checked
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