Migration is a filing-control project

Switching Corporation Tax software is not only a procurement decision. The quality of the first filing season depends on whether the new system has the right prior-year data, client facts, loss schedules, capital allowance balances, supplementary-page history, iXBRL attachments, and approval evidence.

Treat the migration as a controlled CT600 workflow project. The objective is not to copy every old field. It is to preserve the data that affects computation, validation, review, client sign-off, and HMRC submission evidence.

Client and filing identity data

Start with the basics: company name, Companies House number, Corporation Tax UTR, accounting period, registered office, agent authority, and filing responsibility. Keep sensitive identifiers inside the practice system and do not paste them into public support tickets, marketing material, or unprotected notes.

Confirm each active company and which entities are dormant or closed.
Check the accounting period and whether the CT600 period differs from the accounts period.
Confirm who controls Government Gateway or agent submission authority.
Record whether the client needs accounts, computations, CT600, or a full filing package.

Tax history that should move first

The most valuable migration data is the data that changes the next return. Prior-year taxable profit, losses, capital allowance pools, R&D claims, group relief history, repayment claims, and amended-return notes matter more than cosmetic layout in the old system.

Trading loss schedules, including carried-forward and carried-back claims.
Capital allowance pools, additions, disposals, AIA, full expensing, and writing down allowance balances.
Associated-company counts and Marginal Relief assumptions.
Director loan and close company loan history where CT600A may recur.
R&D, creative industry, group relief, or other supplementary-page history.
Open repayments, overpayments, HMRC correspondence, and amendment windows.

iXBRL and attachment readiness

Online Company Tax Returns normally need accounts and computations in the right electronic format. Migration should therefore include the latest accounts production source, final iXBRL accounts, computation working papers, and any notes explaining differences between the accounts and the tax computation.

If the old software generated both accounts and CT600 outputs, check whether the practice is moving those workflows together or only replacing the tax return layer. That decision changes the pilot plan.

Supplementary-page triage

Do not wait until filing week to discover that a client needs a specialist CT600 page. Migration is the right time to tag clients for CT600A close company loans, CT600C group relief, CT600L R&D, CT600P creative industry claims, and any other supported supplementary-page workflow.

Keep unsupported, unusual, or advisory-heavy cases out of the first pilot batch unless the practice has already reviewed them. A clean migration starts with representative but controlled jobs.

How to run the migration in Robocount

Robocount is designed for structured CT600 review rather than a blind import of old software screens. Use the migration to recreate the filing facts that matter, then run the same Compute, Validate, and approval steps that will be used in production.

Create or import client records with the correct period and filing route.
Use Data Entry for trial balance, tax adjustments, losses, capital allowances, and claim data.
Use Supplementary/Indicators to tag specialist CT600 pages before computation review.
Attach prior-year computations, iXBRL, HMRC responses, and client approval records where useful.
Run Compute and compare the result with the old software for a pilot sample before scaling.
Run Validate and keep the differences log as migration evidence.

FAQ

Should we migrate every old CT600 return?

Usually no. Prioritise live clients, open tax history, carried-forward balances, amendment windows, and cases that affect the next return. Archive old filings securely, but do not let archive perfection block the first controlled migration.

What is a sensible pilot batch?

Pick a mix of ordinary trading companies, one dormant or nil case, one capital-allowance-heavy case, and one supplementary-page case that the practice already understands. Avoid the strangest client file as the first test.

Can Robocount replace desktop Corporation Tax software?

Robocount is browser-based Corporation Tax software for CT600 preparation, review, validation, and filing. A migration plan should still confirm accounts production, iXBRL, client approval, and practice file requirements.

Useful official references

This guide is general product and filing workflow information, not tax advice.

Corporation Tax software migration data checklist.