A contractual right to pay an employee a lump sum rather than require them to work out their statutory or contractual notice period. If there is no PILON clause in a contract of employment (www.practicallaw.com/5-200-3117) then an employer who pays an employee a lump sum payment instead of requiring them to work their notice period will be in breach of contract.
For more information, see Practice note, Notice of termination of employment: Payment in lieu of notice.