File your CT600 corporation tax return
HMRC-recognised software for limited companies. Marginal relief, long accounting periods, property companies and CICs all handled automatically. Annual accounts to Companies House included.
Search for your company to start your CT600
Not registered at Companies House? Click here
- HMRC recognised
- Marginal relief built in
- Long periods auto-split
- From £59/year
Built for UK corporation tax
Marginal relief automatic
Profits between £50,000 and £250,000 get marginal relief calculated and the rate shown on your CT600 — no manual tables, no spreadsheets.
Long accounting periods
Periods over 12 months are split into two CT600s automatically, with profit apportioned and computations regenerated for each period.
Property, charity and CIC
Investment companies, CICs, charities and property businesses each get the right boxes, the right reliefs and the right exemptions.
iXBRL accounts included
Filing your CT600 also files your annual accounts to Companies House. One process, one bundle, one price.
Marginal relief calculator
Standalone calculator for sense-checking before you file — same engine as the CT600 itself.
Prior year fetch
Last year's balance sheet is read from your accounts on the Companies House register, so the prior year comparative column is already filled in.
How It Works
From search to submission in minutes
Enter Your Financial Data
Search for your company, select your accounting period, and enter your profit & loss and balance sheet figures. We pre-populate company details from Companies House.
Review Your Documents
Preview your generated accounts and tax computations. See exactly how your corporation tax is calculated. We handle marginal relief, period splitting, and all the complex stuff automatically.
Submit to Authorities
Submit directly to Companies House and HMRC with one click. Track your submission status in real-time and download your filed documents for your records.
More Happy. Tiny Tax.
Corporation tax shouldn't need a textbook. We pull your prior year, calculate marginal relief, split long periods, and submit straight to HMRC. You answer a few questions; we file the CT600. Annual accounts go to Companies House at the same time, free.
Simple pricing — annual accounts included
Every CT600 plan includes Companies House annual accounts filing at no extra cost.
- Solo — £59/year — one company, includes CT600 + annual accounts
- Portfolio — from £99/year — multiple companies (tiered), includes CT600 + annual accounts
- Practice — for accountants filing for clients
Frequently asked questions
Does this also file my annual accounts?
Yes. Solo (£59/year) and Portfolio (£99/year) both include CT600 filing to HMRC and iXBRL accounts to Companies House. There is no separate accounts subscription.
How is marginal relief calculated?
Profits between £50,000 and £250,000 trigger marginal relief at the standard 3/200 fraction, adjusted for accounting period length and associated companies. The full calculation is shown on your CT600 computations document — no manual lookup needed.
My accounting period is longer than 12 months. Can you handle that?
Yes. Periods up to 18 months are automatically split into two CT600 submissions (the first 12 months, then the remainder). Profit is apportioned, computations are regenerated for each period, and both submissions go to HMRC. Accounts are filed once for the full period.
I have a property investment company. Is that supported?
Yes. Property income, property losses brought forward and current-year property losses are all handled — see property company CT600 for the detail.
Are charities and CICs supported?
CICs are fully supported. Charities filing CT600s for trading subsidiaries are supported. We do not currently produce charity SORP accounts — for charity-only filings we file the CT600 but you would need accounts produced elsewhere.
Is this recognised by HMRC?
TinyTax is HMRC-recognised for CT600 filing and submits via the live HMRC Transaction Engine. Recognition is published on the HMRC Corporation Tax compatible software list.