Go to the payroll dashboard (as seen below)

Select the month/week you require >> click view details on the right-hand side >> you will then see the payrun summary >> you can add addition/deductions etc. by clicking the dropdown next to the employee (on the right hand side) >> select add to the field required

Once you are happy with the summary select finalise payrun (top right hand-side) >> then the confirm and proceed or lock for approval buttons will appear, this will also advise you of any warnings, for example the employee is eligible for enrolment to the pension scheme, late submission, below minimum wage etc. >> You can then select lock for approval and send the summary to the company to approve through the employee portal or via email >> 

Whilst the payrun is locked for approval the month will turn blue >> once approved select confirm and submit on the top right hand side >> confirm and proceed and the payrun will be submitted

If submission has not been successful, failed will appear in red on the payrun summary if you view details for that month or on the main dashboard, you can view the reason by going to the paperclip >> HMRC Reports >> select view next to the failed submission >>

in the below example you can see the reason for the failure is the credentials were incorrect i.e., unrecognised HMRC ID’s

To then reopen a payrun, go back to the payrun dashboard >> select the required month/week >> view details >> reopen payrun,this will then allow you to make alterations and re-finalise the payrun