Corporation Tax Compliance Explained (UK 2026)

If you run a limited company in Wolverhampton, Birmingham, or anywhere in the West Midlands, Corporation Tax compliance is critical. Mistakes can lead to HMRC enquiries, penalties, and incorrect tax bills.

At Brightson Accounting, we help limited companies stay compliant while minimizing their tax bills legally. This guide explains exactly what you need to do.

What is Corporation Tax?

Corporation Tax is the tax limited companies pay on their profits.

Current Rate (2026):

• 19% for profits up to £50,000 (Small Profits Rate)
• 25% for profits over £250,000 (Main Rate)
• Marginal relief between £50,000 - £250,000 (effective rate 19%-25%)

You pay Corporation Tax on:

• Trading profits
• Investment income (interest, dividends)
• Chargeable gains (selling assets)

Key Compliance Requirements

1. File a CT600 Return

Every limited company must file a CT600 (Corporation Tax return) annually, even if you made no profit.

Deadline: 12 months after your accounting year-end.

Example: Year-end 31 March 2026 → File CT600 by 31 March 2027.

What's Included:

• Company accounts (profit & loss, balance sheet)
• Tax computation (calculating taxable profit)
• Details of any tax reliefs or allowances claimed

2. Pay Corporation Tax on Time

Deadline: 9 months + 1 day after your accounting year-end.

Example: Year-end 31 March 2026 → Pay by 1 January 2027.

Note: Payment deadline is BEFORE filing deadline. You must estimate and pay tax before submitting the full return.

Late Payment: Interest charged at 7.75% per year (current rate).

3. Keep Accurate Records

HMRC requires you to keep company records for 6 years.

Records must include:

• All sales invoices and receipts
• All purchase invoices and receipts
• Bank statements
• Payroll records
• VAT records (if VAT registered)
• Evidence of capital allowances (equipment, vehicles)

Full guide: Record Keeping Requirements for UK Businesses

Allowable Expenses (What You Can Claim)

You can deduct allowable business expenses from your profit before calculating Corporation Tax.

Common Allowable Expenses:

• Office rent and utilities
• Employee salaries and pensions
• Professional fees (accountant, solicitor)
• Business insurance
• Marketing and advertising
• Travel and subsistence (business only)
• Stock and raw materials
• Equipment (via capital allowances)

NOT Allowable:

• Client entertaining
• Personal expenses
• Fines and penalties
• Political donations

Rule: Expenses must be "wholly and exclusively" for business. Mixed-use expenses (e.g., home office) can be partly claimed. When in doubt, speak to an accountant.

Common Corporation Tax Mistakes

Mistake 1: Missing the Payment Deadline

Many businesses confuse the filing deadline (12 months) with the payment deadline (9 months).

Result: Interest charges accumulate from day 1 of being late.

Solution: Set a calendar reminder for 8.5 months after year-end. Calculate your estimated tax and pay early.

Mistake 2: Claiming Non-Allowable Expenses

Claiming expenses that aren't allowable triggers HMRC enquiries.

We see many West Midlands businesses incorrectly claim:

• Personal holidays as "business travel"
• Home broadband as 100% business (when it's mixed use)
• Expensive client meals as entertaining

Solution: Only claim legitimate business expenses. Keep receipts and justification for every claim.

Mistake 3: Poor Record Keeping

If HMRC enquires and you can't provide evidence, they will disallow expenses and charge penalties.

Solution: Maintain digital records from day one. Use accounting software to track all transactions.

Full guide: Bookkeeping Basics for Compliance

Mistake 4: Not Claiming Capital Allowances

Many businesses forget to claim capital allowances on equipment, vehicles, and machinery.

Annual Investment Allowance (AIA): 100% first-year relief on qualifying assets up to £1 million.

This is a huge tax saving opportunity — but you must claim it correctly.

What Triggers an HMRC Enquiry?

HMRC may investigate your Corporation Tax return if:

• Profits drop significantly year-on-year (without explanation)
• Expense claims seem unusually high for your industry
• You file late repeatedly
• Random selection (HMRC conducts random compliance checks)
• Tips from third parties (customers, suppliers, ex-employees)

How to Avoid:

• File accurate returns on time
• Only claim allowable expenses
• Keep detailed records and evidence
• Work with a qualified accountant

Penalties for Non-Compliance

Full guide: HMRC Penalties Explained: How to Avoid Them

How Brightson Accounting Can Help

We help limited companies across Wolverhampton and the West Midlands with:

• Corporation Tax return preparation and filing
• Tax computation and planning (minimizing your bill legally)
• Accurate accounts preparation
• Capital allowances claims
• HMRC enquiry support

Want to stay compliant and reduce your corporation tax at the same time? We specialize in both.