The publish date refers to the date Payslips are made available to employees. If sending email notifications has been selected during the upload process, the emails will also be sent on this date.
You can amend the publish date during the upload process. If the payslips have already been uploaded then you will need to re upload the payslips ensuring the payslip date remains the same. As long as the Payslip date is the same this will overwrite the existing payslips, if a different date is used, new payslips will be generated.
Please note, if you choose to change the publishing date by re uploading the payslips, it is possible that the welcome email may still be sent out on the original publish date so you may need to send out a manual company wide email, advising employees their payslips are available.