Hi @mduh
I've come to the conclusion that ATUM is a purchase order system, not an accounting system. The Purchase Price field works OK if you only treat it as an input for purchase orders, and all suppliers apply VAT to B2B supplies identically to B2C sales. That is the case in the UK, but maybe less so in the EU.
Because of ATUM's previous change in tax behaviour, I repurchased the official WC Cost of Goods plugin, and now manually insert ex-VAT prices in that field, while the ATUM Purchase Price is inc. VAT. The WC CoG plugin has quite good reporting in WC Reports for inventory valuation, which is the important thing that I lost when ATUM changed. There is also the profit reporting you are looking for, although it is limited use for me, due to affiliates.
But of course, none of this is true FiFo valuation. To do that, you need to treat each block of stock coming in as a separate "batch", and I am not sure it is likely that batch/expiry management and compliant FiFo valuation are coming anytime soon in ATUM. So I expect the next move for me to be to one of those big expensive inventory management platforms.