Payments are money received from a Customer. Payments for specific Invoices are handled in the Cash Receipts module, while Payments from a Customer that aren't applied (i.e. prepayments) are handled in Credits.

To add a new Cash Receipt, click new, and type or search for a Customer, then select the Payment Type. The amount to receive can then be typed in manually, or if the Auto Calculate box is checked, then the amount will come from the total applied to all the Invoices ticked in the Outstanding Invoices section. Enabling the Allow Overpayment option and entering a Total greater than the checked Invoices will create a credit for the amount unapplied.

Once the Payment is created, the Received tab will display all Invoices the current payment applies to.

Credits are raised in the Cash Receipt module by receiving an amount but not applying it to any Invoices. The list view of the Credits module displays all unapplied credits currently in the system.

To pay an Invoice using Credit, enter the Billing Customer in the top of the Credits module detail view, and on the appropriate Credit record, use the Invoice Number dropdown to specify which invoice to pay (this list will only display outstanding invoices for the current Customer). Clicking Save will apply the whole credit or pay the whole Invoice (which ever is lower), or you can manually set an amount to apply using the Amount Applied field then clicking Save.