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Ftax for Businesses

Corporation Tax for limited companies

Tax filing with iXBRL for companies

Generate both iXBRL account and computation files, and submit company tax and VAT returns to HMRC with ease. Optionally, use a cashbook to populate incomes and expenses in either a micro entity or small companies accounts template. 

All required forms are included in Ftax for Businesses.

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Ftax Business Company CT600

Ftax Business Company CT600 (2025/26)

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iXBRL

  • Included with the Ftax CT600
  • Both iXBRL computations and accounts generated
  • Templates for micro entities and small companies
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Cashbook

  • Low cost online accounting
  • Record incomes, expenses, and other business data
  • Populates the VAT, SA100, SA800, and CT600 forms
Learn more

Filing a CT600

Running a limited company means filing a Company Tax Return (CT600) and paying Corporation Tax (CT) on your profits. Since 1 April 2023, CT is tiered: 19% on profits up to £50,000, 25% above £250,000, and a marginal relief band in between so your effective rate rises gradually. If you have associated companies, you split those £50k/£250k limits between you. Ring-fenced oil & gas profits have separate rules.

Do I pay Corporation Tax?

You do if you’re a UK limited company (or a non-UK company with a UK branch) and you make taxable profits from:

  • Trading (your day-to-day business),
  • Investments (e.g. interest, some rents),
  • Chargeable gains (selling assets for more than tax value).

You register for Corporation Tax within 3 months of starting to trade (not just when you incorporate). HMRC will post your UTR to the registered office soon after incorporation.

Current rates & thresholds

Profits (after reliefs)

Rate

Notes

Up to £50,000

19%

“Small profits rate”

£50,000–£250,000

19–25%

Marginal relief tapers the effective rate up

Over £250,000

25%

“Main rate”

Associated companies: If you control or are controlled by other companies (outside a 51% group), divide the £50k/£250k limits by the number of associates. Limits are also time-apportioned if your accounting period is <12 months.

Tip: The marginal relief formula can be tricky; use HMRC’s calculator to get the exact effective rate.

What goes in the CT600?

Your CT600 reports the accounting period (max 12 months) and your tax computation, including:

  • Profit per accounts: tax adjustments (add back disallowables like client entertainment; deduct capital allowances; apply loss relief and other claims).
  • Chargeable gains on asset disposals (after indexation ends, but with usual reliefs where available).
  • Reliefs/credits claimed (e.g., R&D where applicable, creative industry reliefs, charitable donations).
  • Loans to participators (s455) if you’ve lent money to shareholders/directors of a close company.

You must attach:

  • iXBRL-tagged statutory accounts, and
  • iXBRL-tagged tax computation.

Returns are filed online.

Long first year? Companies House may allow accounts >12 months, but corporation tax can’t.

You’ll file two CT600s covering that period.

Corporation Tax Deadlines

  • Pay Corporation Tax: 9 months + 1 day after the end of your accounting period (if profits are at or below the £1.5m “large company” threshold, divided by associated companies and time-apportioned).
  • File CT600: 12 months after the end of your accounting period.

Large/Very Large companies (QIPs):

  • If (augmented) profits > £1.5m (divided), pay by quarterly instalments.
  • If > £20m (divided), “very large” rules pull instalments earlier into the year.

Penalties & interest:

  • Late filing: automatic £100, then another £100 at 3 months; at 6 months HMRC can estimate the bill and add a 10% penalty of unpaid tax; another 10% at 12 months. Repeat late filers see the £100s rise to £500.
  • Late payment: HMRC charges interest from the due date; repayment interest applies if you’ve paid too early.

Paying your bill

Pay electronically (Faster Payments/CHAPS for same or next-day; Bacs/Direct Debit take longer). Plan around weekends and bank holidays so funds clear on time. If cash flow is tight, speak to HMRC about a Time to Pay arrangement before the due date.

Records you must keep

Keep for 6 years (or longer if returns are under enquiry):

  • Full accounts and working papers,
  • Sales/purchase records,
  • Fixed asset and capital allowance schedules,
  • Loss memoranda (what arose, what used/carried forward),
  • Evidence for reliefs claimed
  • Any group/associated company details affecting thresholds.

Common pitfalls

  • Disallowables: client entertainment, most fines/penalties, asset depreciation (use capital allowances instead).
  • Director’s loan still outstanding 9 months after year-end? You may owe s455 (currently 33.75%), repayable when the loan is cleared.
  • Associated companies overlooked: can push you into marginal relief or instalments sooner than expected.
  • Two returns for a long first period missed: it’s a common cause of penalties.

Pre-filing checklist

  • Registered for CT and have your UTR
  • Accounts finalised; capital allowances reviewed
  • Losses/reliefs optimised (and elections noted)
  • Associated companies counted and limits apportioned
  • iXBRL tagging for accounts and computation complete
  • CT600 totals agree to the computation
  • Payment scheduled (right method, right date)

Ready to file?

Ftax Business Company CT600

Ftax Business Company CT600 (2025/26)

1 Credits
£85.00
More Info
Buy Now

Disclaimer

Ftax does not provide accounting, tax, business or legal advice. This guide has been provided for information purposes only. You should consult with your own professional advisors or with HMRC for advice directly relating to your business before taking action in relation to any of the content provided. Ftax Support will only be able to assist you with matters directly concerning the Ftax products and service.

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