Currently it’s perpetual weighted average method. Mostly because it handles edge-cases that FIFO and LIFO does not.
For example, how would you treat landed costs? Or if you have multiple divisions selling goods on the same day. How would you objectively decide which specific inventory items were sold by each division?
In both cases, usually you end up averaging costs for all inventory items. And then it’s no longer FIFO or LIFO. You might as well go all the way and just use perpetual weighted average method.
Saying that. I want to implement more flexibility to inventory costing if required. But FIFO and LIFO has its own problems too.