No need to figure out the new prices to account for a credit, with this integrated functionality just wait until you make another order to the same vendor, and enter the quantity.
This can also be used when a store wants to 'exchange' some product. If this is the case, just think of it as two separate transactions.
First, the store will create what's called a 'return manifest', after which, you will be able to receive the items back into your inventory. After receiving them (via the Inbound/Returns button) you'll be able to view or modify the refund value here: https://app.getgrowflow.com/Reports/D/InboundTransfers.
Next, if you 'owe' the store for the returned product, and you'd like to issue them the credit, simply type it into the 'Credit' line on the next Invoice that you send them. Remember, the next products you sell them will still be at normal prices, but the Invoice will show them the applied credit.
To keep it really obvious and easy for your store and bookkeeper, we recommend to also add a note to the invoice like this:
Note: These Credits do not effect the 'Traceability' prices on your Sales Reports. Credits should only be used when the Store returned some faulty product via their own manifest.
If you instead need to apply a 'Discount' for example at a Vendor Days you sold some stuff but now need to 'back date' a discount, they should be handled via the normal 'Discount' feature, and will be tracked inside of the Traceability system.