Associated Companies on CT600
Report associated companies on Box 326 — TinyTax scales marginal relief thresholds automatically
Why Use This Feature?
How It Works
Enter the number of associated companies (excluding this one)
TinyTax divides the £50k and £250k thresholds by the company count
Marginal relief is recalculated against the scaled thresholds
Box 326 is populated on the CT600 we file with HMRC
Tax due reflects the adjusted bands
Who Benefits?
Companies in a Group
Holding company plus subsidiaries? Each one is associated and shares the £50k/£250k thresholds. TinyTax scales correctly when you set the count.
Multiple Companies Same Owner
A director with two unconnected limited companies — they're still associated for HMRC purposes. TinyTax handles the division automatically.
Quarter-Period Associations
A company that joined or left the group mid-period needs the right associated count. TinyTax accepts the number that applied during the period.
Frequently Asked Questions
What counts as an associated company?
A company is associated with another if one controls the other, or both are controlled by the same person. The HMRC definition includes voting rights, share capital, and director appointment rights — see HMRC manual CTM03900 for the detail.
How does it affect my tax?
Each associated company divides the £50k lower limit and £250k upper limit. With one associated company, your thresholds become £25k and £125k — meaning marginal relief kicks in at lower profits.
Where do I declare associated companies on CT600?
Box 326 on the standard CT600 (number of associated companies). TinyTax populates this from the count you enter on the form, and the marginal-relief threshold split uses the same value across trading, property, and Mixed Income (advanced) filings. Box 625 (Number of 51% group companies) is a separate CT600 field reported in the FII / investment-holding context for Mixed Income — not a substitute for Box 326.
Does it apply to dormant associated companies?
Generally, dormant companies don't count as associated. The exception is companies that became dormant during the accounting period — they may still count for part of it. Check with your accountant if unsure.
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