Associated Companies and Corporation Tax

1. Why Associated Companies Matter

From 1 April 2023, corporation tax has three rates: 19% on profits up to £50,000 (the small profits rate), 25% on profits above £250,000 (the main rate), and a marginal rate of 26.5% between the two thresholds (after the mechanics of marginal relief). The £50,000 and £250,000 thresholds are per company, but only if the company stands alone.

Where a company has one or more associated companies, both thresholds are divided equally between all the associates. Two associated companies: £25,000 lower and £125,000 upper each. Three: £16,667 and £83,333. The intention is to prevent owners fragmenting a business across multiple companies to stay below the thresholds. The effect for legitimate group structures is a stealth tax rise from April 2023 that many owner-managed groups are only noticing at year-end.

2. The Association Test

Two companies are associated for an accounting period if, at any time in that period, one has control of the other, or both are under the control of the same person or persons. The test is broad: control at any point in the period counts, even for a single day.

Association is not limited to UK companies. Overseas companies under the same control as a UK company count. Dormant companies do not count (see excluded companies below). The test runs outward from each UK company separately, so the number of associates depends on whose perspective you're taking.

3. What Counts as Control

A person controls a company if they are able to exercise direct or indirect control, through share capital, voting rights, rights to income, or rights to distributions on a winding-up. The statutory test uses an "either-or" approach: anyone who holds more than 50% of any one of those measures controls the company.

This is a lower bar than many owner-managers assume. A director-shareholder owning 51% of Company A and 51% of Company B controls both and the two are therefore associated, even if each company has an entirely unrelated minority investor. The practical consequence: a portfolio of owner-managed SPVs is almost always a single associated-company family.

4. Attribution to Associates

The rules attribute the rights of a person's associates to them when measuring control. Associates for this purpose include:

• Spouse or civil partner.
• Siblings.
• Parents and grandparents.
• Children and grandchildren.
• Business partners.
• Trustees of settlements where the person is a settlor or beneficiary.

Substantial commercial interdependence test: HMRC will not treat two companies as associated solely because of family attribution unless there is "substantial commercial interdependence" between them, financial, economic, or organisational. A husband and wife each running entirely separate businesses with no trading, financing, or management overlap are generally not treated as running associated companies, even though the attribution rules would formally link them. The burden of evidence falls on the taxpayer.

5. Excluded Companies

Not every commonly-controlled company counts against the threshold. Ignored associates include:

• Dormant companies. A genuinely dormant company (no significant accounting transactions and filing dormant accounts) does not count. Useful for holding companies that hold only a fixed investment.
• Passive holding companies whose only activity is holding shares in a 51% subsidiary and does not otherwise trade.
• Non-trading companies with no income/gains. Relevant to dissolution runs.
• Companies that become associated only via the attribution rules where there is no substantial commercial interdependence (see above).

6. Worked Example

A director owns three companies outright: TradeCo (profits £40,000), PropertyCo (profits £30,000), and ConsultancyCo (profits £35,000). All three are actively trading and commercially linked (shared premises, shared bookkeeping, inter-company invoicing).

7. Practical Planning Response

• Dissolve or formally dormant any shell companies that aren't serving a purpose. A £10 dormant-accounts filing per year costs far less than the marginal-relief drag of keeping a defunct company on the register.
• Consolidate trades where it makes commercial sense. If three operating companies genuinely share resources, merging into one can unlock a single full £50,000/£250,000 band, subject to commercial, liability, and VAT considerations.
• Consider whether a holding company needs share capital. A passive holding company ignored under the exclusions is better than a small-trading associate that dilutes everyone's threshold.
• Avoid "convenience" SPVs. Setting up a separate company for one contract or one property is now a measurable tax cost, not a free admin layer.
• Document substantial commercial independence where spouse/family companies operate on genuinely separate tracks. Clear contemporaneous evidence (separate premises, separate clients, separate bookkeeping, no cross-trading) is the test HMRC applies.
• Time associates carefully. A company acquired or incorporated mid-period still reduces the thresholds for the full period. Plan incorporations at the start of an accounting period where possible.

Our corporation tax service maps every group structure's associates at onboarding, and flags dormant or near-dormant companies that are quietly costing the group marginal relief.