Does Ketto issue 80G receipts to the donors on our behalf?

No, the 80G receipt will be issued to Indian donors by you. You will be provided with a dashboard that will have all your donors' details auto-populated and a tool to send bulk 80G receipts with 1-click.

Do we have to issue the 80G receipt on the amount donated by the donor or how much we receive?

The receipt will have to be issued on the gross amount donated by the donor, not the net amount you receive post deductions. The total deduction counts as fundraising/overhead charges.