In lieu means “instead of” or “in substitution for” something that would otherwise be due under a legal right or obligation. In UK and Irish legal practice it is a descriptive expression, not generally a defined term, and appears across many contexts (for example, “payment in lieu”, “benefit in lieu”, “in lieu of notice”, “in lieu of arrestment”, “in lieu of dower/legitim/portio debita”). In employment law, a “payment in lieu of notice” (PILON) is a sum paid instead of requiring the employee to work their notice period. Its availability and tax treatment depend on contract terms and applicable statutory rules. In property and commercial law, a party may accept money or some other consideration “in lieu” of performance, damages, or specific rights (for instance, a sum in lieu of reinstatement, or compensation in lieu of an easement). Courts will examine the parties’ agreement and the surrounding legal framework to determine whether the substitution is valid and what rights are waived or preserved. Usage and legal effect of “in lieu” are broadly consistent across England and Wales, Scotland, Northern Ireland and Ireland, with differences arising from the specific underlying doctrine or statute.