when is employer liable to make payment in lieu of not serving notice?

If an employer terminates a employee by issuing termination letter and there was no notice by employer, When is the employer liable to pay the money in lieu of the notice - is it to be pid alongside with termination letter or same day when termination withoit notice issues to employee?or can it paid a day after termination? If the paymnet in lieu of notice was paid one day after termination, then can the employer force employee to return all company assets immediately when the payment (in lieu of ntice) was still pending at the time of termination letter being served to employee?