>Hi,
> I am developing POS (Point od Sales) system. My client request to have feature that able to view the stock balance at the particular period such as 2 months ago or may be 2 days ago.
> How could I retrieve the stock qty at certain period? Should I re-calculate the total purchase, total return, total sales of items in order to get these stocks balance?? What do you do for these?
>
>Thank you

Hi John,

Without knowing :
A. what kind of stock
B. how fast it moves
C. if inventory is frozen during counts
D. security of the inventory
E. How much the people at the clients site actually believe the figures
F. and especially without knowing exactly for what the client is really asking... I'll jump in anyway.

A transaction file that records every addition and subtraction of inventory and a balances file are very good types of tables to keep. A stock balance is then very easy to determine for any moment of any day for as far back as you keep transaction records.
The balances file would be useful for storing actual physical inventorys as of a certain date and could also be used to store a balance for any purgings of the transaction file.

I'd recommend that you investigate inventory tracking methods either from books in your local library or from www.apics.org (Am. Production and Inventory Control Society) for a good solid basis in inventory control. Even a couple of hours of reading will stand you in good stead.