Why CT600 software matters to practices now

The closure of the joint HMRC and Companies House filing service has made commercial Corporation Tax software more important for directors and small companies. For accountants, that creates a familiar problem: more clients arrive needing CT600 help, but the practice still has to protect review quality and deadline control.

Good CT600 filing software should make Corporation Tax production repeatable. It should help the practice move from client records to reviewed return, not just from typed boxes to a submission button.

The practice workflow to standardise

A strong practice workflow separates collection, preparation, review, client approval, filing, and post-filing evidence. When those stages blur, returns become harder to review and harder to explain.

Client intake: company identity, UTR, accounting period, Companies House status, deadlines, agent authority, and prior-year position.
Accounts and source data: trial balance, accounts, tax-sensitive ledgers, adjustments, losses, and relief claims.
Computation: profit adjustment, capital allowances, losses, credits, rates, and tax payable.
Supplementary-page review: CT600A, CT600C, CT600L, CT600N, CT600P, and other specialist pages where facts require them.
Attachment readiness: iXBRL accounts and computations, plus any supporting documents required for the return.
Approval: preparer review, partner or manager sign-off, and client approval before submission.
Submission: Government Gateway filing, HMRC response, rejection handling, and evidence saved to the file.

Do not treat supplementary pages as edge cases

Supplementary pages are part of the Company Tax Return and are covered by the declaration. They should not be added at the end of the job because a box looked relevant. The practice needs an early checklist.

Common owner-managed-company triggers include:

overdrawn directors' loan accounts or other close company loans that may require CT600A;
group companies claiming or surrendering losses through CT600C;
R&D claims or credits that need CT600L review;
residential property development activity that may bring CT600N into scope;
creative industry reliefs and expenditure credit claims that may require CT600P.

The filing software should make those triggers visible while the computation is being prepared, not after the return has already been approved.

What reviewers need to see

A reviewer needs a route from the source records to the CT600 boxes. For straightforward companies, that may be a short trail. For complex companies, it may include multiple schedules, claims, and supplementary pages.

the accounting period covered by the return;
the source accounts and computation basis;
adjustments from accounting profit to taxable profit;
reliefs and claims included or deliberately excluded;
supplementary pages included and the reason for each one;
iXBRL attachment status;
client approval and final submission evidence.

Migration from desktop tax suites

Many practices still run CT600 work through older desktop tax suites, spreadsheets, shared drives, and separate approval emails. That can work at small scale, but it creates friction when teams are remote, staff change, or clients expect faster filing.

Browser-based CT600 software should reduce handoff friction. The aim is not to remove professional judgment. It is to keep the data, calculation, review notes, supplementary-page decisions, and submission status in one place.

Practice-specific buying questions

Can junior preparers and senior reviewers work in the same return without exporting files back and forth?
Does the product support the supplementary pages your client base actually uses?
Can it handle both simple director-led companies and more specialist company cases?
Does pricing punish team access, or can the whole practice use the workflow?
Does it give enough audit trail for review, rework, and HMRC query response?
Can it support structured intake or API-led workflows as the practice automates more of the job?

How Robocount supports accountant CT600 work

Robocount is designed for accountancy practices that want a focused Corporation Tax workflow. It keeps the CT600 package at the centre: main return, supported supplementary pages, computation, attachments, review, and submission readiness.

Unlimited team-seat style workflow for practice collaboration.
Supported CT600 supplementary pages visible from the return review flow.
Browser-based preparation and review rather than desktop file handoff.
Government Gateway submission workflow for supported returns.
API and MCP-native surfaces for practices building automation around CT600 work.

FAQ

What should accountants look for in CT600 filing software?

Look for the full return package: CT600, computations, iXBRL attachments, supplementary pages, review evidence, client approval, and HMRC submission handling. A form-only workflow is rarely enough for practice production.

Does every client need supplementary pages?

No. But the practice should check the facts early. Supplementary pages become part of the Company Tax Return when included, and HMRC's warning and declaration framework applies to them.

Can directors still self-file?

Directors can use suitable commercial software, but many will need help where accounts, computations, director loans, claims, or supplementary pages are not straightforward.

Is Robocount an accounts suite?

Robocount is focused on UK Corporation Tax and CT600 filing workflows. It is designed to work around the tax return package rather than replace every practice system.

Useful official references

This guide is general product and filing workflow information, not tax advice. Practices should check current GOV.UK guidance and the client's facts before filing.

CT600 filing software for accountants: a practical workflow checklist.