Trial questn

In my view you are talking about Tally in this regard you should mention closing balance in Opening Balance every month then you show the closing balance.

If the valuation is done before preparing trial balance, then the following entry is passed and accordingly the adjusted account's balance shown in Trial Balance :

Stock-in trade A/c              Dr.

      To Purchases

I agree with Mr. Stranger, he explains to you in deeply and follow to him.   

Dear,

In simple, if any entry has not been passed related to closing stck till preparence of trial balance

then no clsk stk (dr bal) would be stood in trial baln. but after its valuation at last following 

adjustment to be follow i.e clos stk a/c dr To Trading A/c & closing stk shown in b/s (asset side).

by passing 1st entry closing stks ledger shows dr balnce hence it will be stud in b/s.