The allowance method involves setting aside a reserve for bad debts that are expected in the future. The reserve is based on a percentage of the sales generated in a reporting period, possibly adjusted for the risk associated with certain customers. For example, if the historical bad debt experience has been 3% of sales, and the current month’s sales are $1,000,000, then the bad debt reserve to be set aside is $30,000. The allowance is adjusted over time to more closely match actual experience.
By creating this allowance, bad debt expenses are being matched against sales within the same period, so that readers of the financial statements will have a better understanding of the true profitability of sales.
The mechanics of the allowance method are that the initial entry is a debit to bad debt expense and a credit to the allowance for doubtful accounts (which increases the reserve). The allowance is a contra account, which means that it is paired with and offsets the accounts receivable account. When a specific bad debt is identified, the allowance for doubtful accounts is debited (which reduces the reserve) and the accounts receivable account is credited (which reduces the receivable asset). If a customer subsequently pays an invoice that has already been written off, then the process is reversed to increase both the allowance and the accounts receivable account, after which the cash account is debited to increase the cash balance and the accounts receivable account is credited to reduce the receivable asset.
The alternative to the allowance method is the direct write-off method, under which bad debts are only written off when specific receivables cannot be collected. This may not occur until several months after a sale transaction was completed, so the entire profitability of a sale may not be apparent for some time. Thus, the direct write-off method is a less theoretically correct approach to dealing with bad debts.