An employer can treat an employee’s wages or any occupational maternity or sick payments as payments towards SMP, or the other way round if:
If these payments are less than the SMP due the employer must make up the difference.
Payments funded by employees cannot be offset against an
employer’s liability to pay SMP.
If payment is paid from a jointly funded scheme, and it
counts as earnings for NICs purposes, that part of the payment
funded by the employer, can be offset against the employer’s
SMP liability.