When adding stock for parts, it is possible to connect the added stock to an existing order, or create a new order on the fly. PartsBox will then maintain information about where the parts were acquired from. In plans with lot control, that information will be connected to a specific lot, and in all other plans it will apply to the part.
Orders have ID Anything™ codes, which can be printed and attached to invoices, for quick future retrieval of order data.
There are many BOM tools out there, but most of them deal only with a single Project/BOM. In real life, however, one sometimes needs to plan production of several devices. Since their BOMs often share parts, it isn't always easy to determine what actually needs to be purchased, especially given that you might already have some of the parts.
Meta-parts (part alternates) make this even more complicated: until the moment of ordering you want to be flexible as to the choice of a specific MPN (Manufacturer Part Number).
Purchasing in PartsBox makes the ordering process much easier: