Question

why we deduct old provision from bad debts in profit and loss A/c???

Answer 1

we made provision for bad debts to handle bad debts.So in case bad debts occur we have to reduce that amount of provision of bad debts from bad debts because we are already in a position to handle that loss.

Answer 2

The amount of provision for doubtful debts on the one hand side is shown on the debit side of profit and loss account an on the other side is deducted from the debtors on the asset side of balance sheet so that the debtor may appear at their realizable value in the balance sheet.It will be shown in the profit and loss .
Hope it helped!!