To collect offline payment, login from superadmin/admin panel then go to Online Course > Offline Payment here select Class, Section and Student and click on the Search button, after searching record all the courses will be listed below of the page.
Now click on the Pay button of the course for which you want to collect payment, at click of this button Online Course Fee modal will open, here enter select Date, Payment mode and click on the Pay button.

collect offline fee

Once payment is collected you will see Revert button instead of Pay button, by clicking this Revert button you can revert fee amount.

revertoffline fees image

To print pay slip click on the Print button present in the Action column.

print ofline payment payslip

Note If you revert the course then student progress will be 0.