UK Employer Rules · 2026
Can my employer stop me joining a competitor after I leave?
Legal basis
Common law restraint of trade doctrine; Mason v Provident Clothing 1913 (foundational case); Tillman v Egon Zehnder 2019 (UK Supreme Court severance principles); pending Restrictive Covenants Bill (2024 consultation).
When they CAN do it
Your employer CAN enforce a restrictive covenant if: (1) you signed it (or it was in your contract); (2) it protects a legitimate business interest (confidential information, customer connections, stable workforce); (3) it's reasonable in geographical scope (usually limited to areas where you actually worked); (4) it's reasonable in duration (3-12 months is typical, longer is hard to enforce); (5) the activity restricted is genuinely competitive; (6) consideration was given (usually the job itself, though variations may need separate consideration).
When they CANNOT do it
Your employer CANNOT: enforce overly broad clauses ('all UK', 'all industry sectors', '24+ months'); enforce against employees who didn't have access to confidential info or key clients; restrict you from working in roles that aren't genuinely competitive; enforce clauses you signed under duress; enforce clauses that have been varied without fresh consideration; enforce post-employment if the dismissal was wrongful or unfair (employer's repudiatory breach voids the covenant).
What you should do
1) Get a copy of your contract IMMEDIATELY when planning to leave — covenants can be hard to access later. 2) Take specialist advice — many employment lawyers offer fixed-fee covenant review (£300-£500). 3) Consider scope: geographical, time, activity. Wider = less enforceable. 4) Approach your new employer about indemnity for legal costs (common in senior roles). 5) Don't take confidential info, client lists, or proprietary materials. 6) If your old employer threatens enforcement, force them to court — most don't proceed because of cost and uncertainty. 7) Be willing to negotiate a reduced restriction.
Worked example
Sophie's contract had a 12-month UK-wide non-compete. She wanted to join a competitor in a different city. Lawyer advised the geographical scope was unenforceable (she'd only worked in one region) and the duration disproportionate (only 6 months would be reasonable for her role). Old employer sent threatening letter; Sophie's lawyer responded citing Tillman case. Old employer didn't proceed. Sophie joined competitor; nothing happened.
Red flags — when to escalate
🚨 Very wide geographical scope ('UK-wide', 'global'). 🚨 Long durations (18+ months for non-senior roles). 🚨 Restrictions on whole industry sectors. 🚨 Cascading covenants (non-compete + non-solicitation + non-dealing all stacked). 🚨 Refusal to discuss scope. 🚨 Threats before you've even resigned.
Recruiter pro tip
The vast majority of restrictive covenant threats never make it to court — litigation is expensive (£50,000+) and judges scrutinise these clauses ruthlessly. Most senior moves involve some form of negotiated release (old employer waives in exchange for confidentiality and non-solicit of named accounts). If you're being recruited, ask the new employer to indemnify you for any litigation costs — many will, especially for senior hires. The proposed 3-month statutory cap (if enacted) will further weaken existing covenants.
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