UK Subsidiary Audit: When the Group Decides for You

Higher audit thresholds took effect for financial years beginning on or after 6 April 2025. For a UK subsidiary audit, that change often makes no difference at all.

The reason is straightforward. Your size is not judged on your own accounts. It is judged across the whole group, worldwide. A UK company with £3 million of turnover and twelve staff can still need a statutory audit. The cause is a large parent in Chicago or Munich.

Many UK finance teams find this out late. They read the new limits and assume they are exempt. The group auditor tells them otherwise in week one of the group timetable.

What Actually Decides a UK Subsidiary Audit

Three things sit between you and audit exemption, and they apply in order.

• The group size test: the whole group must qualify as small, measured on aggregate figures across every entity, wherever it sits.
• The ineligible group rules: if any group company is a bank, insurer, MiFID investment firm or traded company, exemption is gone.
• The two-year rule: status changes only once the position has held for two consecutive financial years.

Shareholders holding 10% or more can also demand an audit. So can a lender, as a condition of facility. Neither appears anywhere in the Companies Act size tests.

The Parent Guarantee Route Is Closed to Most Overseas Groups

Section 479A of the Companies Act 2006 offers a separate exemption. A subsidiary inside a large group can skip its audit where the parent guarantees its liabilities.

There is a catch many groups have not caught up with. The parent must be established under the law of some part of the United Kingdom.

Before Brexit, an EEA parent qualified. It no longer does. A parent in the United States, Germany or Japan does not qualify. Nor does any other parent outside the UK.

Where a UK intermediate holding company exists, the route may reopen. The guarantee under section 479C is a real legal commitment. It covers all the subsidiary’s liabilities for the year and cannot be withdrawn. Groups planning to sell the subsidiary should think hard before using it.

Your Group Auditor Will Ask for More Than Before

ISA (UK) 600 was substantially revised. The old split between significant and non-significant components has gone.

In its place sits a risk-based approach applied to every component. Component auditors are now formally part of the group engagement team. Responsibility for their work rests with the group engagement partner.

For a UK entity that means more requested procedures and more documentation. It also means a file the group auditor can review and stand behind, on a timetable set elsewhere. The group cannot sign until the components are done.

Why This Is Harder Than It Looks

The technical position is only half of it. The practical problem is fit.

Group audit instructions arrive in the group’s own house style. Materiality is set centrally. Deadlines often bear no relation to your Companies House filing date. They assume the local auditor can absorb reporting packages and turn round clearance within days.

A local firm without group experience can deliver a perfectly sound statutory audit and still fail that test. When it happens, the group auditor escalates. The UK entity then changes auditor mid-cycle, under time pressure. That is an expensive way to find out.

There is an accounting angle too. Lease capitalisation under the revised FRS 102 applies to periods beginning on or after 1 January 2026. Balance sheet totals rise as a result. Companies sitting near a threshold can cross it with no change in the underlying business.

How Hamlyns Can Help

We act as component auditor for UK arms of overseas groups. It is work we do regularly and it suits us.

Our first job is to tell you whether you need an audit at all, group test and section 479A included. We deal directly with your group auditor, in their format and to their deadlines. Statutory accounts and the CT600 are handled alongside, so the UK entity has one point of contact rather than three. Where the answer is that no audit is required, we say so.

If your parent’s auditor has been in touch, or your UK filing deadline is closing in, get in touch with the Hamlyns team. You may also want to read our piece on the audit threshold change, or our summary of transfer pricing reporting for UK subsidiaries.