When ever you given the advance the same was shown in the Loans & advance (Current Assets). now the same has been convert in to 'Bad Debts' and should be dr in P/L a/c.
As you had paid money as advance to some one against sales. If any goods delivered him against the advance it will be consider in to sales, but there was no movement of goods and the advance is also not received back. So that it will consider as an expenses and accounted under 'Bad Debts' or ' Sundry Balance Written off" . this will impact that the Dr balace of the debtors is now cleared.
1 At the time of Paymant of Advance
Customer/Debtor A/c Dr.
To Cash/ Bank
2. At the time of Written Off
Bad Debts/Sundry Balance Written off A/c Dr.
To Customer/Debtor A/c
If still teher is any confusion then you may refer the primary books of account and also you can search the IT provision at incometaxindia.gov.in.