Bad debts

Bad debts 係已確認的壞賬. 因此直接由應收賬中撇銷.
Dr Bad debts Cr. Accounts Receivable

Doubtful debts係有可能收不到的呆賬, 所以做provision for doubtful debts.

Dr Profit and loss account Cr Provision for doubtful debts.

Bad debts means the amount already irrecoverable from the debtors. The amount is immediately written off from the debtors' balance and recognized as an actual expense in Profit and Loss Account.
Doubtful debts means the amount are not certain and just an estimate from the past experience that a certain percentage of debts may be bad at the end. In accounting, as a principle of prudence, we usually provide a certain percentage on the total amount of the debtors as bad and / or doubtful. In balance sheet, we usually present it as Debtors less Provision for Bad and Doubtful Debts.