Tax Implications of Mergers and Acquisitions in the UK: A Practical Guide

The way an acquisition is structured can change the tax outcome significantly, for both buyer and seller. In the UK, the central choice is almost always between a share deal and an asset deal. These two structures create different tax positions on stamp duty, Capital Gains Tax, goodwill, and inherited liabilities. This guide covers the key UK-specific tax considerations for business owners and advisers navigating mergers and acquisitions in 2025-26.

Share Deal vs Asset Deal: The Central Tax Question

Every acquisition starts with the same fundamental question: are you buying the shares of the company, or are you buying the underlying assets and trade? The tax consequences diverge significantly.

Business Asset Disposal Relief (BADR) for Sellers

For owners selling a qualifying business, Business Asset Disposal Relief (BADR), formerly Entrepreneurs’ Relief, is the most significant tax planning tool available. In 2025-26, BADR reduces the Capital Gains Tax rate on qualifying gains to 14% on the first £1,000,000 of lifetime gains (the rate rose from 10% in October 2024 and will rise again to 18% from April 2026).

To qualify for BADR on a share sale, the individual must:

• Have owned at least 5% of the company’s ordinary shares and voting rights for at least two years before disposal
• Have been a director or employee of the company for at least two years before disposal
• Be selling shares in a trading company (or holding company of a trading group)

Important: BADR rates are changing. The 14% rate applies for disposals in 2025-26 (6 April 2025 – 5 April 2026). From 6 April 2026, the rate rises to 18%. Business owners considering a sale should take advice on timing, as the difference on a £1 million gain is £40,000 in additional CGT from April 2026.

Stamp Duty and SDLT, Costs Buyers Often Underestimate

Stamp Duty on Share Transfers

Stamp Duty at 0.5% applies to the consideration paid for UK shares transferred via a paper stock transfer form. It is rounded up to the nearest £5. Transfers via CREST (electronic settlement) attract Stamp Duty Reserve Tax (SDRT) at 0.5% with no rounding.

On a £5 million share acquisition, Stamp Duty would be £25,000. This is often overlooked in deal modelling, particularly when deferred consideration is involved, as stamp duty is payable on all known consideration at completion, including earn-out amounts that can be ascertained.

SDLT on Asset Deals Involving Land and Property

If an asset deal includes commercial property, Stamp Duty Land Tax (SDLT) applies to the property element. Commercial SDLT rates in 2025-26 are 0% up to £150,000, 2% on £150,001–£250,000, and 5% above £250,000. In a mixed deal, the property and non-property consideration must be separated carefully.

Goodwill: The Post-2015 Restriction

In asset deals, the price paid typically includes goodwill, the value attributed to brand, customer relationships, and business momentum above the fair value of tangible assets. For accounting purposes, goodwill is capitalised and amortised. However, for tax purposes, the treatment changed materially for acquisitions after July 2015.

Post-July 2015, the Corporation Tax deduction for amortisation of purchased goodwill was largely abolished. This means a buyer in an asset deal that allocates a large portion of the purchase price to goodwill may receive no Corporation Tax relief on that amortisation. Careful allocation of purchase price between goodwill, customer contracts, brand, and tangible assets is essential to maximise deductible depreciation.

Exception: Companies buying goodwill from an unrelated third party where the goodwill relates to intellectual property may qualify for relief under specific provisions. This is a technical area and requires specialist tax advice.

Inherited Tax Liabilities in Share Deals

When you buy shares, you buy the company’s history,  including its tax history. A buyer in a share deal takes on:

• Any underpaid Corporation Tax from prior periods
• PAYE and NIC liabilities, including any historic IR35 exposure
• VAT assessments or underpaid output tax
• Any HMRC enquiries in progress at the date of completion

This is why tax due diligence is critical in any share acquisition. The findings inform tax warranties and indemnities in the Share Purchase Agreement (SPA),  the legal protections that allow the buyer to claim back losses from the seller if undisclosed liabilities materialise post-completion.

Corporation Tax Losses

Pre-acquisition trading losses in the target company can only be used against future profits if there is no major change in the ownership and nature of the trade (under the anti-avoidance rules in CTA 2010). Buyers who are attracted to a target partly because of significant brought-forward losses should take advice early, HMRC may challenge the use of those losses if the trade changes materially post-acquisition.

Group Relief and Post-Acquisition Integration

Once a target company joins a group (broadly, 75% common ownership), group relief provisions become available:

• Trading losses in one group company can be surrendered to offset profits in another
• Assets can be transferred between group companies without immediate Corporation Tax or CGT
• VAT grouping may be available, simplifying intra-group transactions

These provisions make post-acquisition integration more tax-efficient, but require careful structuring, particularly around loan relationships and the degrouping rules that apply if a company later leaves the group.

A Note on Jurisdiction

This guide covers the UK tax framework for M&A. There is no equivalent of US C-corporation or S-corporation structures in UK law, and the UK does not operate a long-term/short-term capital gains distinction based on a holding period. UK CGT applies regardless of how long you have held an asset, with BADR providing a rate reduction on qualifying business disposals, not a holding period reduction.