CT600 supplementary pages explained

Supplementary pages are extra parts of the CT600 that you add only when a particular situation applies. Most small companies need none. The two that come up most often are CT600A, for loans to directors and shareholders, and CT600L, for research and development.

Last checked against GOV.UK on 1 October 2026.

A4O Accounts prepares the CT600 from your books and files it with HMRC. See the CT600 software, or get started free.

How supplementary pages work

The main CT600 asks, in its “About this return” section, which supplementary pages are attached. Each page has its own boxes, and its result is carried to a box on the main form. They’re part of the same return, sent at the same time. You don’t file them separately.

If you’re new to the form, see what is a CT600 first.

The full list

These are the supplementary pages GOV.UK lists with the CT600:

There’s no CT600G in the list, and no CT600O.

The pages a small company is most likely to need

CT600A: loans to directors and shareholders. If a company controlled by its directors or a handful of shareholders lends money to one of them, and the loan is still outstanding at the end of the period, CT600A reports it and works out the tax due on it. An overdrawn director’s loan account is the usual cause. See CT600A explained.

CT600L: research and development. Companies claiming R&D relief or the R&D expenditure credit complete CT600L with the return. See CT600L explained.

CT600C: group and consortium relief. If your company is in a group and one company’s losses are set against another’s profits, the claim or surrender goes on CT600C.

CT600E: charities and Community Amateur Sports Clubs. For charities and clubs claiming exemption from tax.

The rest are for specialist situations: overseas subsidiaries, shipping, oil and gas, insurance, large property developers, and film, television, games and theatre production.

Checking your software covers the page

GOV.UK’s list of commercial software for Company Tax Returns shows which supplementary pages each product supports. Check it before you start a return, because a page your software can’t produce means the return can’t be filed from it. More on this in choosing CT600 software.

Which pages A4O Accounts supports

A4O Accounts supports CT600A and CT600L. You add either page on the return’s tax computation, and a CT600L’s R&D deduction counts in the computation once the page is attached. The other supplementary pages aren’t supported, so a return that needs one, such as a group relief claim on CT600C, can’t be filed from A4O Accounts yet. See CT600 software for what is and isn’t covered.

More in this series: all the CT600 guides.