EXCESS MONEY RECEIVED ON SALE OF GOODS

Excess Amount received from customer should be shown in Balance Sheet under the heading Sundry Debtors (though it will have Credit balance)
Reason :-
1st altertative:-
Excess amount received doesn't belongs to you and the same is refunded hence when it is refunded the ledger will get closed by passing Debit entry..

2nd alternative:-
If another sales invoice is raised then excess amount can be adjusted against that invoice and difference will be payable by your Customer .

3rd altertative:-
if suppose the client doest demand for 2000 and also in future he doesn't purchase goods from you then in that case transfer thd amount in p&l a/c as income...

In case of 3rd Alternative:-

what is the GST implication of the amount transferred to P&L a/c ?