Forcing a SMP payment through the system is very easy to do.
To force SMP through on a worker:
Click Payroll, then select Statutory Payments Maintenance.
Select SMP History Maintenance, then, to enter Modify Mode, press Ctrl+M.
Select the Use Override check box, then enter the calculated Overridden Value.
Change the Force SMP Payable drop-down to YES.
Run the Statutory calculation as normal.