Bad debt expense is estimated and recorded in the period of sale to correspond with the matching principle. Subsequent write-offs of specific accounts do not affect the expense further. Rather, both the asset and the allowance for doubtful accounts are decreased at that time. If a written off account is subsequently collected, the allowance account is increased to reverse the previous impact. Estimation errors are to be anticipated; perfect predictions are rarely possible. When the amount of uncollectible accounts differs from the original figure recognized, no retroactive adjustment is made if a reasonable estimation was made. Decisions have already been made by investors and creditors based on the original data and cannot be reversed. These readers of the statements should have understood that the information could not possibly reflect exact amounts.