Fastbase

There are number of options to consider.

1.
If the invoice has not yet been sent out, then maintain the invoice, make any price changes and re-print the invoice.

For further details on maintaining an invoice see How do I change a customer invoice after it has been generated? and for details on re-printing an invoice see How do I reprint an invoice/credit note?.

2.
Create a Customer Credit and credit the item/s that were overcharged. Now recharge the item/s at the correct price on a new invoice.

This option is recommended as it is the most accurate option (the methods below work but have their drawbacks).

3.
Create a customer credit. Ignore the existing line items on the credit note. Add a new line item with the part MISC (or any other non-diminishing, non-stock item), quantity 1 and price (this should be the amount by which the customer was overcharged).

This option does not correctly update the gross profit reported under the stock sales analysis report. The overcharged item will be showing a sale at the original sale price and therefore the GP% will be overstated. The MISC item will show a -ve gross profit.

4.
Enter a Customer Journal for the overcharged customer. Analyse this to the Sales GL Account. The Amount entered should be the amount by which the customer was overcharged and the Tax should be inclusive of gst.

This option does not alter the gross profit shown under the customer or the stock items, ie: the gross profit reported will show the profit based on the original sale price. Only the General Ledger will show the correct sales value.

It is recommended that the journal only be used for small amounts, for example to fix rounding differences or other minor discrepancies.