CT600 for Contractors and Freelancers: Complete Tax Filing Guide 2026

Corporation tax filing as a contractor or freelancer operating through a personal service company (PSC) presents unique challenges. From navigating IR35 rules to optimising your dividend-salary split, your CT600 requires careful attention to industry-specific rules that generic guides simply don't cover.

This comprehensive guide walks you through everything IT contractors, consultants, and freelancers need to know about filing their CT600 in 2026 — with practical advice you can actually use.

What Makes Contractor CT600 Filing Different?

If you run a PSC — the standard operating model for UK contractors and freelancers — your CT600 isn't like filing for a typical trading company. Here's why:

• IR35 status directly affects how income flows through your company and what ends up on your CT600
• Dividend vs salary extraction is central to your tax strategy and CT600 figures
• Expense patterns are unique — home office, travel, equipment, training, and professional subscriptions
• Revenue concentration often comes from one or two clients, creating specific reporting considerations
• Flat Rate VAT interactions need careful CT600 treatment

Most contractor PSCs are small companies with straightforward accounts — which means you can absolutely file your CT600 without an accountant. But you need to understand the contractor-specific nuances.

IR35 and Your CT600: What You Need to Know

Outside IR35

If your contracts are outside IR35, your company receives gross income from clients. This is the traditional PSC model, and your CT600 will report:

• Turnover — the full invoiced amount to your clients
• Salary costs — whatever salary you've paid yourself (typically the optimal director's salary)
• Employer NIC — a deductible expense for corporation tax
• Pension contributions — if you make employer contributions (a highly tax-efficient extraction method; see our pension contributions relief guide)
• Business expenses — all allowable expenses your company has incurred
• Trading profit — the figure that ends up in Box 155

The remaining profit after corporation tax is available to extract as dividends — the core of the dividend vs salary strategy.

Inside IR35

If your contract is inside IR35 (whether determined by the client under the off-payroll rules, or by you for smaller clients), things change significantly:

Client determines IR35 status (medium/large clients):

• The end client or agency deducts PAYE tax and NIC before paying your PSC
• Your company receives a net payment after those deductions
• On your CT600, you report this net amount as income
• You claim a credit for the tax and NIC already paid via the deemed employment payment
• The 5% allowance for expenses still applies — claim this on your CT600

You determine IR35 status (small clients):

• Your company receives gross income
• You must operate the deemed payment calculation at year end
• The deemed salary, employer NIC, and apprenticeship levy are calculated
• These become deductible expenses on your CT600
• Only the residual amount remains as company profit

Pro tip: If you have a mix of inside and outside IR35 contracts, keep meticulous records of which income relates to which. Your CT600 needs accurate figures for both streams.

For a deeper dive, see our dedicated CT600 for contractors: IR35 guide.

The Optimal Salary and Dividend Strategy for Your CT600

Your salary and dividend decisions directly impact your CT600 figures. Here's the 2025/26 tax-efficient approach:

Recommended Salary Level

The sweet spot for most contractor directors in 2025/26 is a salary at the NIC Primary Threshold of £12,570 per year (£1,047.50/month). This:

• Uses your full personal allowance
• Avoids employee NIC (starts at £12,570)
• Employer NIC at 15% is payable above £5,000 (the Secondary Threshold), costing approximately £1,136 — but this is a deductible expense on your CT600
• Preserves your State Pension qualifying year

Some contractors set salary lower at the Lower Earnings Limit (£6,396) to avoid employer NIC entirely while still getting a qualifying NI year. The right choice depends on your overall tax position.

How This Appears on Your CT600

The remaining post-tax profit sits in your company until you extract it as dividends.

Pension Contributions — The Secret Weapon

Employer pension contributions are one of the most tax-efficient tools for contractors:

• Fully deductible against corporation tax on your CT600
• No NIC for employer or employee
• No personal income tax until you draw the pension
• Annual allowance of £60,000 (2025/26), with potential carry-forward of unused allowance from previous 3 years

If your PSC has strong profits, maximising pension contributions before year end reduces your CT600 liability significantly.

Contractor Expenses: What to Claim on Your CT600

Contractors have specific expense patterns. Here's what's allowable and how to report it:

Home Office Costs

Most contractors work from home at least some of the time. You can claim:

• HMRC flat rate — £6/week (£26/month) without receipts
• Actual proportion — calculate the business percentage of your home costs (mortgage interest/rent, utilities, broadband, council tax). Requires records but often gives a higher deduction
• Dedicated office space — if you rent a room or have a dedicated office, the deduction can be more substantial

This reduces your trading profit on the CT600, lowering your corporation tax bill.

Travel and Subsistence

Contractor travel is a contentious area. The rules:

• Temporary workplace travel (under the 24-month rule) is fully deductible
• Client site travel — deductible if the engagement is temporary
• Mileage — 45p per mile for the first 10,000 miles, 25p thereafter if using your personal car
• Hotels and meals when working away from your normal base — deductible if wholly and exclusively for business

Warning: If you're inside IR35, the 5% flat-rate expense allowance covers travel and most other costs. You can't claim individual expenses on top.

Professional Development and Subscriptions

• Training courses that maintain or update existing skills — deductible
• Professional body memberships (BCS, IET, RICS, etc.) — deductible
• Technical books, online subscriptions (cloud services, dev tools) — deductible
• Training for an entirely new skill unrelated to current work — not deductible

Equipment and Technology

• Laptops, monitors, keyboards, desks — claim via capital allowances or the Annual Investment Allowance
• Software subscriptions (Microsoft 365, GitHub, AWS) — deductible as revenue expense
• Mobile phone (business use) — fully deductible if company contract; proportion if personal contract

Professional Indemnity and Insurance

• Professional indemnity insurance — fully deductible
• Public liability insurance — fully deductible
• Director's personal accident insurance — may be a benefit in kind

Filing Your Contractor CT600: Step by Step

Step 1: Gather Your Records

Before you start, you'll need:

• Bank statements for the full accounting period
• Invoices issued to all clients
• Expense receipts organised by category
• Payroll records — RTI submissions showing salary paid
• Dividend vouchers — dates and amounts of all dividends declared
• VAT returns — to reconcile turnover figures
• Previous CT600 — for comparison and loss carry-forward

Check our complete records guide for the full list.

Step 2: Prepare Your Accounts

Your company accounts form the basis of the CT600. For most contractor PSCs (qualifying as micro-entities), you'll prepare:

• Profit and loss account — income less expenses equals profit
• Balance sheet — assets (cash, debtors) less liabilities (tax, creditors, directors' loans)
• These need to be in iXBRL format for filing

Step 3: Complete the CT600

For a typical contractor PSC, you'll fill in:

• Boxes 1-30 — Company details, accounting period, turnover
• Box 145 — Net trading profits before capital allowances
• Box 155 — Trading profits (the big one)
• Box 235 — Profits chargeable to corporation tax
• Box 440 — Tax payable
• Boxes 525-530 — Tax already paid (if quarterly instalments apply)

For the full picture, see our CT600 box-by-box guide.

Step 4: File and Pay

• File your CT600 within 12 months of your accounting period end (see deadline guide)
• Pay corporation tax within 9 months and 1 day of your accounting period end
• Don't miss the deadline — penalties start at £100 and escalate quickly

Flat Rate VAT and Your CT600

Many contractor PSCs use the Flat Rate VAT Scheme. This creates an important interaction with your CT600:

Under the flat rate scheme, you charge clients 20% VAT but pay HMRC a lower percentage (typically 14.5% for IT consultants, or 16.5% in the first year with the 1% discount). The difference is profit to your company.

On your CT600:

• Include the flat rate VAT surplus as income — this is taxable trading income
• Report your turnover excluding VAT (the net figure)
• The VAT surplus gets added to your profit calculation

See our detailed guide on Flat Rate VAT and Corporation Tax for worked examples.

Important: Since April 2017, many contractors fall into the "limited cost trader" category (16.5% flat rate), which reduces but doesn't eliminate the VAT surplus.

Directors' Loan Account: The Contractor's Trap

Many contractors use their directors' loan account as a convenient way to take money from the company. Be careful:

• If your loan account is overdrawn (you owe the company money) at year end, the company must pay Section 455 tax at 33.75% — reported on your CT600
• This is a temporary tax — repaid when you repay the loan — but the cash flow impact is significant
• Many contractors accidentally overdraw their account by taking "drawings" without declaring dividends first

Best practice: Declare dividends formally before withdrawing cash, and reconcile your loan account monthly.

Corporation Tax Rates for Contractors (2025/26)

Most contractor PSCs have profits between £20,000 and £100,000. Here's how the rates work:

Watch out for associated companies — if you have more than one company (e.g., a holding company and a trading company), the thresholds are divided. Two associated companies means the small profits rate applies only up to £25,000.

Use our corporation tax calculator to work out your exact liability.

Year-End Tax Planning for Contractors

Smart contractors plan their CT600 before their year end. Key strategies:

1. Maximise pension contributions — reduce taxable profit with employer contributions
2. Time your equipment purchases — buy before year end to claim capital allowances in the current period
3. Review salary level — ensure you've paid the optimal salary
4. Declare dividends — clear any director's loan account balance
5. Consider the marginal rate — if profits are between £50,000 and £250,000, marginal relief makes every pound of expense reduction worth more

Check our year-end planning tips for the complete checklist.

FAQ: CT600 for Contractors and Freelancers

Do I need to file a CT600 if I had no contracts this year?

Yes. If your company is registered for corporation tax, you must file a CT600 even with zero income. File a nil return to stay compliant.

Can I claim training costs on my CT600?

Training that maintains or updates your existing professional skills is deductible. Training for entirely new, unrelated skills is not. An IT contractor taking an advanced AWS certification? Deductible. The same contractor taking a plumbing qualification? Not deductible.

What if I have both inside and outside IR35 contracts?

Report both streams of income on the same CT600. For inside IR35 income from medium/large clients, report the net amount received and claim credit for PAYE/NIC deducted. For outside IR35 income, report the gross invoiced amount. Keep separate records for each.

How much does it cost to file a CT600 as a contractor?

Accountant fees for contractor PSCs typically range from £800 to £2,000+ per year. With Taxpipe, you can file for just £59 — the accounts preparation, iXBRL conversion, and HMRC submission are all included.

Can I claim the cost of my accountant/filing software on my CT600?

Yes. Accountancy fees and tax filing software costs are fully deductible business expenses.

Do I need supplementary pages for my CT600?

Most contractor PSCs only need the core CT600. You may need supplementary pages if you have: overseas income, chargeable gains, loans to participators, or R&D tax credit claims.

What's the deadline for my contractor CT600?

Your CT600 is due 12 months after your accounting period end. If your company year runs April to March, your CT600 for the year ending 31 March 2026 is due by 31 March 2027. But corporation tax payment is due by 1 January 2027 — 9 months and 1 day after year end. See our deadline guide.

Can I carry forward losses from a bad year?

Yes. If your company made a trading loss, you can carry it forward indefinitely to offset against future trading profits. You can also carry it back one year. This is reported on your CT600 and can eliminate your tax bill in profitable years.

File Your Contractor CT600 with Taxpipe

As a contractor, you understand efficiency. You bill by the day, and spending days wrestling with HMRC's filing requirements isn't a good use of your time — or your money.

Taxpipe is built for contractors like you:

• £59 flat fee — not the £1,000+ an accountant charges. See pricing →
• HMRC-recognised filing software — your CT600 goes directly to HMRC
• iXBRL accounts generated automatically — no extra cost
• Step-by-step guidance — designed for directors, not accountants
• 15-minute filing — answer questions in plain English, we handle the tax form

You've done the hard part — running your contracts, keeping your records, managing your expenses. Let Taxpipe handle the filing.

Start filing your CT600 now →

Use our corporation tax calculator to see exactly what you'll owe before you file.

This guide is for general information and does not constitute tax advice. For complex IR35 situations or unusual circumstances, consider consulting a specialist contractor accountant. Taxpipe makes CT600 filing simple for straightforward contractor companies — try it today.

Related Reading

• Corporation Tax for Contractors: IR35 and Your CT600
• Dividends vs Salary: The Tax-Efficient Way to Pay Yourself
• Dividend vs Salary: The Most Tax-Efficient Split for 2025/26