An account becomes uncollectible a. when an account receivable is converted into a note receivable b. There is no general rule for when an account becomes uncollectible. c. when a discount is availed on notes receivable d. at the end of the fiscal year

The correct answer is letter "B":  There is no general rule for when an account becomes uncollectible.

Explanation:

Accounts Uncollectible represent any form of debt as a result of sales on credit that are likely not to be paid. Before classifying debt as uncollectible there is an unset timeframe that may go by.  

At first, the sale on credit is considered an account receivable with a payment promise usually of 30 or 90 days. If three month passes but no payment is received, the account is considered aged receivables but if more time goes through without payment, the account then is labeled as doubtful.  

Doubtful accounts become allowances if the company decides to take care of the payment of the debt with its own profit. There is no set rule when an account receivable becomes uncollectible. It relies on the judgment of the firm.