CT600M guide

CT600M: Freeports and Investment Zones in the CT600 workflow.

A practical guide for companies and accounting practices preparing CT600M claims for Freeport and Investment Zone tax sites, enhanced allowances, site evidence, and reviewer sign-off.

What CT600M is for

CT600M is the Company Tax Return supplementary page for Freeports and Investment Zones. HMRC guidance covers enhanced structures and buildings allowances and enhanced capital allowances in qualifying sites.

This page is used to capture the site, expenditure, allowance, and qualifying-activity detail that supports the Corporation Tax return. It should be reviewed alongside the capital allowances computation and the main CT600.

When CT600M normally appears

CT600M is relevant where a company is claiming Freeport or Investment Zone relief through the CT600 package. The key question is not simply whether the business is near a Freeport or Investment Zone; the claim needs qualifying expenditure, qualifying activity, and the required site-level evidence.

Before filing, practices should usually confirm:

  • The site is a relevant Freeport or Investment Zone tax site for the claim.
  • The accounting period covered by CT600M does not exceed 12 months.
  • The expenditure is split correctly between enhanced structures and buildings allowances and enhanced capital allowances.
  • The claim has enough supporting detail for each building, structure, or asset pool.
  • The CT600 computation and capital allowances schedules agree with CT600M.

Enhanced structures and buildings allowances

HMRC's CT600M guidance asks for separate entries for claims relating to each building or structure. That means a strong workflow should not collapse several site projects into one unexplained total.

Reviewers should be able to trace the qualifying spend, the building or structure, the site basis, and the amount claimed. If a practice imports fixed asset data, the import should preserve the project-level evidence needed for CT600M.

Enhanced capital allowances

CT600M can also capture enhanced capital allowance claims. These should tie back to the fixed asset register, the qualifying-site evidence, and the Corporation Tax computation.

The common trap is treating a Freeport or Investment Zone label as enough. The review should confirm the asset, expenditure date, qualifying use, site connection, and claim amount before the page is filed.

When this is not the right page

Do not use CT600M for ordinary capital allowances that are not connected to a Freeport or Investment Zone claim. Do not use it just to describe a trading location. The page belongs to specific relief claims that need supporting site and expenditure detail.

If the company has ordinary plant and machinery allowances, structures and buildings allowances, or annual investment allowance claims outside these regimes, the claim belongs in the main computation rather than CT600M.

Evidence trail for practices

CT600M claims are evidence-heavy because the claim depends on where the activity happens and what expenditure qualifies. A reviewer should not have to infer the site status from a project name.

  • Keep the Freeport or Investment Zone tax-site evidence used for the claim.
  • Retain invoices, fixed asset records, and project schedules for qualifying expenditure.
  • Map each CT600M entry to the related building, structure, or asset pool.
  • Reconcile CT600M claims to the capital allowances computation.
  • Document excluded expenditure and ordinary capital allowance treatment separately.

Example review scenarios

Company operates near a Freeport

Location alone does not prove eligibility. Check whether the activity and expenditure relate to a qualifying tax site and whether the specific allowance conditions are met.

Fixed asset import includes Freeport-tagged assets

Treat the tag as a starting point. The filing file still needs supporting evidence, qualifying-site analysis, and reconciliation to the capital allowances computation.

How Robocount handles CT600M workflow

Robocount treats CT600M as a structured part of the capital allowances and CT600 review process. The workflow is designed for browser users, API integrations, and AI-assisted filing where the source data must remain explainable.

  • Tracks Freeport and Investment Zone site detail in the CT600M page.
  • Separates enhanced structures and buildings allowances from enhanced capital allowances.
  • Pre-populates company and accounting-period header data from the main return.
  • Connects CT600M values to capital allowances review checks.
  • Keeps evidence and reviewer sign-off visible before filing.

FAQ

Is CT600M only for Freeports?

No. HMRC's current guidance and form title cover Freeports and Investment Zones.

Does a company need CT600M just because it trades in a Freeport area?

Not automatically. CT600M is tied to qualifying claims and supporting site and expenditure detail, not a simple location label.

Can CT600M cover more than one building or asset?

Yes, but the review should preserve separate entries and supporting evidence where HMRC guidance asks for separate claim detail.

Useful HMRC references

This guide is general product and filing workflow information, not tax advice. Check the latest HMRC guidance and the company's qualifying-site evidence before filing.