What to do if your costs vary in time

[C]

Do you know how to solve this issue? because if my costs change and I change them in the back office i will affect the historical data, 

[Andy]

hello. The changes of Cost will not influence previose sales data. 

[kst]

How about this scenario? 

Lets say i have 10 pieces of item A with cost 1 dollar purchased 10 days ago. 

I have since sold 8pcs and i am left with 2pcs today. 

Today i added 10 more pieces of item A with cost 1.50. 

The cost reflects 1.50 per pc in Loyverse which is wrong from an accounting view. If using average cost, the cost should be [(1.50 x 10) + (1 x 2)] / 12 = 1.42. If using FIFO, the cost should still remain 1 dollar until i sell off the remaining 2 pcs, only then will cost change to 1.50. 

I would love to subscribe to advanced inventory module if the inventory valuation report is correct (but from my testing from trial period its not as my inventory cost prices vary for different lots). My accountant reject the valuation generated from loyverse thus I have to use a separate system for inventory but i would love to be able to work with just one system. 

Please help. 

[Andy]

Hello. If you use advanced inventory management, than the average cost is calculating in the way as you have described. 
https://help.loyverse.com/help/advanced-inventory-management