I’m sorry to bring up this topic again but it appears FIFO costing is not applying correctly.
In a clean file on v25.12.2.3146:
- create inventory item with FIFO costing
- create 3 purchase invoices on 3 different dates to buy a total of 3 units at different cost
- recalculate inventory cost
- create 3 sales invoices on 3 different dates to sell all 3 units
- for sales invoice #1, Manager calculated the average cost from the 2 previous purchase invoice instead of the earliest one. It uses ($5+$10)/2 = $7.50, instead of just $5
- for sales invoice #2 and #3, Manager treats the total inventory cost of the 2 remaining qty as ($5+$10+$20-$7.50)/2 = $13.75, instead of $10+$20 = $30
None of the COGS on the 3 sales invoice have the correct FIFO COGS. It’s also not a simple average cost over time. Manager is using average cost of available units at time of sales invoice to build cost layers.