You can send a Thank you note to your customers for their timely payments by following these steps,
1) Automating Thank you notes for online payments,
2) Customizing thank you notes,
3) Acknowledgement for offline payments,
You can also choose to send out a thank you note optionally each time you manually record a payment made to you offline. While selecting ‘Record payment’ on an invoice , just manually check the box saying ‘Send a thank you note for this payment’ to do this.
4) Alternatively, to acknowledge payments made by customers for whom you’ve enabled client portal, just comment a quick thank you right on the particular invoice page once for which you’ve received their payment. This can be seen by the contact since the client portal allows them to view their estimates and invoice page details.
and GST filing.