Purchase Prefix is the information positioned in-front of the Purchase Order, we use “PO-” as your default, you can change this through your settings otherwise it is set to start start from PO-00001.
It is possible to automatically increase the Purchase Order number sequentially for you. You may want us to start doing this from a particular number, you can do this in the Web Portal.
Settings cog > Accounts > Purchases > Prefix and Automatic Sequence Numbering.
To update this in the App > Settings > Purchases.