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Corporation Tax

The CT600 computation, boxed from the books you already have

Finn builds the CT600 computation from the accounts already prepared in AccountsOS: the boxes, the iXBRL-wrapped accounts, and the full filing package to download. Filing to HMRC is being enabled. Until then, download the package and file it through your existing agent software, no re-keying the figures.

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Only MTD VAT is HMRC-recognised today. CT600 submission is not yet enabled.

Coming soon

Tax layer on AccountsOS: The CT600 computation and filing package, built from the accounts you already prepare.

AccountsOS · The computation, boxed

The Corporation Tax screen showing Finn's prepared CT600 computation with the boxed figures, the iXBRL preview and a download-package button

How it works

How it works

01

Finn builds the computation

Once the annual accounts are prepared, Finn runs the current UK Corporation Tax rates against the profit figure: small profits rate, main rate, and marginal relief in between.

02

You add what Finn can't see

Capital allowances, R&D relief and losses brought forward are adjustments only you or the client can confirm. Finn never estimates them.

03

The boxes and the iXBRL, together

The CT600 boxes and the iXBRL-wrapped accounts are built from the same source, so the figures on both agree with each other and with the books.

04

Download the package

The computation, the iXBRL accounts and the XML package download together. File through your existing agent software while HMRC submission is being enabled.

  • The CT600 boxes computed from the accounts already prepared in AccountsOS
  • The current small profits rate, main rate and marginal relief, kept up to date
  • Capital allowances and losses brought forward are adjustments you confirm, never guessed
  • The iXBRL accounts and the CT600 computation come from the same source figures
  • Download the full package today, submission to HMRC is being enabled

FAQ

The questions accountants ask first

Can I file the CT600 straight to HMRC from AccountsOS?

Not yet. AccountsOS has HMRC recognition for MTD VAT, not for the Corporation Tax Online service. Download the prepared package and file it through your existing agent software until that changes.

Where do the figures in the computation come from?

The same annual accounts you already prepare in AccountsOS for Companies House. The CT600 is built from that profit figure, not typed in separately, so the two never disagree.

Does Finn apply capital allowances or R&D relief on its own?

No. Those are judgement calls only you or the client can make. Finn leaves them as explicit adjustments you enter, never a guess folded into the computation.

What does the downloaded package actually contain?

The boxed computation as a readable summary, the iXBRL-wrapped accounts, and the CT600 XML package, the same three things your filing software would otherwise need typed in by hand.

What about Self Assessment or MTD for Income Tax?

Scoped, not built yet. AccountsOS already computes a director's personal figures for reference on the Self Assessment page, but there is no SA100 or MTD ITSA filing path in AccountsOS today.

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