Post-Transaction Legalities UK: Buyer & Seller Duties
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Signing the sale and purchase agreement feels like the finish line, but in reality it is closer to a starting pistol. Once the ink dries on a UK business sale or share purchase, both sides inherit a fresh set of legal duties that rarely get the attention they deserve in the rush to complete.
Warranty claim windows begin to run, indemnity triggers become live, Companies House filings fall due, and certain contractual promises continue long after completion. Getting these post-completion steps right protects the value of the deal for the buyer and limits exposure for the seller.
This guide, written from a civil and commercial law perspective, walks through the main areas that tend to catch parties out in the weeks and months after a transaction closes, and explains where speaking with an experienced legal adviser can help you think through your own situation.
Overview
Post-transaction legalities are the legal, regulatory and contractual obligations that survive completion of a business sale, share purchase or asset acquisition. They sit in the gap between signing and genuinely 'done', and they apply whether the deal was a small owner-managed business sold to a trade buyer or a larger share sale with institutional involvement.
The obligations typically fall into four buckets: warranty and indemnity positions set out in the sale agreement; ongoing contractual restrictions such as non-compete, non-solicitation and confidentiality undertakings; statutory filings and notifications, including those required by Companies House and HMRC; and continuing governance duties for directors under the Companies Act 2006. Some duties sit with the seller, some with the buyer, and some with the company itself.
Missing a deadline, overlooking a disclosed risk or failing to honour a continuing covenant can unwind commercial value quickly, sometimes leading to claims under the sale agreement or regulatory consequences. Understanding what applies, and when, is the foundation of a clean post-completion period.
Key steps
- Diarise every key date in the sale agreement. The warranty claim period, any earn-out milestones, deferred consideration payments, tax covenant limitation dates and restrictive covenant durations all run from completion. Put each one in a calendar with reminders well before the deadline, so nothing expires by accident and no payment is missed. 2. Complete statutory filings and registrations promptly. Share transfers, changes to persons with significant control, director appointments or resignations, and new registered office details must be filed with Companies House within the relevant time limits. Stamp duty on share transfers, where it applies, must also be dealt with before the register of members can be properly updated. 3. Work through the disclosure letter and warranty position carefully. The disclosure letter qualifies the warranties, so the buyer should review it alongside due diligence findings to identify any issues that may support a claim. The seller should keep the disclosure bundle safe as evidence of what was disclosed, in case a claim is made later. 4. Honour continuing contractual covenants. Non-compete, non-solicitation and confidentiality clauses typically continue for a defined period after completion. Sellers should understand exactly what they cannot do, where and for how long, and buyers should monitor compliance so that any breach can be addressed while remedies remain realistic. 5. Keep directors focused on their statutory duties. Directors of the target company continue to owe duties under the Companies Act 2006, including the duty to promote the success of the company under section 172. Post-completion board changes, updated authorities, and fresh decision-making processes should be documented in proper board minutes.
Common questions
If you're dealing with this kind of situation, a call with an experienced legal adviser can help you work out the right next step — from £89.
Common questions
Q How long does a buyer usually have to bring a warranty claim?
The sale agreement sets the answer. General commercial warranties often have a shorter limitation period, while tax warranties and the tax covenant tend to run longer, reflecting HMRC's own assessment windows. Exact periods are negotiated deal by deal, so the contract itself is the authoritative source. Missing a contractual deadline usually bars a claim, even where the underlying breach is clear, so diary management matters.
Q What is the difference between a warranty and an indemnity?
A warranty is a contractual statement about the business that, if untrue, gives rise to a damages claim on ordinary contract principles, meaning the buyer must prove loss. An indemnity is a promise to reimburse the buyer pound-for-pound if a specified risk materialises, without the usual hurdles of proving loss or mitigation. Indemnities are typically used for known or identified risks, while warranties cover the general state of the business.
Q Do restrictive covenants on a seller always hold up?
Not automatically. English courts will enforce restrictive covenants given by a seller of a business where they protect a legitimate interest, such as goodwill, and go no further than reasonably necessary in scope, geography and duration. Covenants on sellers are generally easier to enforce than equivalent covenants in employment contracts, but drafting that is too wide can still be struck down. Each case turns on its facts.
Q What filings does a buyer need to make at Companies House after a share purchase?
Common post-completion filings include updating the register of persons with significant control, filing any appointments or resignations of directors and the company secretary, updating the registered office if it is changing, and confirming the information at the next confirmation statement. Share transfers themselves are recorded internally in the register of members rather than filed directly, but related filings often follow. Deadlines vary, so check gov.uk for the current time limits.
Q Who is responsible for pre-completion tax liabilities?
In a share sale the company continues to carry its historic tax liabilities, which is why buyers usually insist on a tax covenant (sometimes called a tax deed) requiring the seller to pay the buyer an amount equal to pre-completion tax liabilities that were not provided for. In an asset sale the position is different because liabilities generally remain with the selling entity. The sale agreement will set out exactly who bears what.
Q Do directors' duties change after a company is sold?
The statutory duties under the Companies Act 2006 continue to apply to whoever is a director of the company at the relevant time. What often changes is the composition of the board, the shareholder base those duties are exercised for, and any group dynamics where the company becomes part of a larger structure. New directors should be briefed on their duties, and proper board minutes should document decisions from day one after completion.
Q What happens if a warranty turns out to be misleading after completion?
The buyer's first step is usually to check whether the issue was fairly disclosed against the warranty in the disclosure letter, because a fair disclosure typically blocks a claim. If not, the buyer should review the notification requirements in the sale agreement, which often require written notice within a set period and in a specified form. Failing to follow the notice mechanics can defeat an otherwise strong claim.
If you're dealing with this kind of situation, a call with an experienced legal adviser can help you work out the right next step — from £89.
Sources
This guide is based on primary UK law and official guidance.
- LegislationCompanies Act 2006legislation.gov.uk
- LegislationCompanies Act 2006, section 172 (duty to promote the success of the company)legislation.gov.uk
- Guidance · Companies HouseCompanies House filing requirementsgov.uk
- Guidance · HMRCStamp duty on sharesgov.uk
- LegislationSale of Goods Act 1979legislation.gov.uk
Legal helpline
Unsure what to handle after your deal completes?
Post-completion obligations can sit quietly for months before causing problems, from missed filings to overlooked restrictive covenants. An experienced legal adviser can talk through your specific situation on the phone and help you think about what to prioritise based on what you describe.
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Legal disclaimer
This article is for general information only. It is a tool to help you find your way — not legal advice, and not a substitute for speaking to a qualified adviser about your situation.