26 CFR § 1.166-4 - Reserve for bad debts.
(a) Allowance of deduction. A taxpayer who has established the reserve method of treating bad debts and has maintained proper reserve accounts for bad debts or who, in accordance with paragraph (b) of § 1.166-1, adopts the reserve method of treating bad debts may deduct from gross income a reasonable addition to a reserve for bad debts in lieu of deducting specific bad debt items. This paragraph applies both to bad debts owed to the taxpayer and to bad debts arising out of section 166(f)(1)(A) guaranteed debt obligations. If a reserve is maintained for bad debts arising out of section 166(f)(1)(A) guaranteed debt obligations, then a separate reserve must also be maintained for all other debt obligations of the taxpayer in the same trade or business, if any. A taxpayer may not maintain a reserve for bad debts arising out of section 166(f)(1)(A) guaranteed debt obligations if with respect to direct debt obligations in the same trade or business the taxpayer takes deductions when the debts become worthless in whole or in part rather than maintaining a reserve for such obligations. See § 1.166-10 for rules concerning section 166(f)(1)(A) guaranteed debt obligations.
(b) Reasonableness of addition to reserve -
(1) Relevant factors. What constitutes a reasonable addition to a reserve for bad debts shall be determined in the light of the facts existing at the close of the taxable year of the proposed addition. The reasonableness of the addition will vary as between classes of business and with conditions of business prosperity. It will depend primarily upon the total amount of debts outstanding as of the close of the taxable year, including those arising currently as well as those arising in prior taxable years, and the total amount of the existing reserve.
(2) Correction of errors in prior estimates. In the event that subsequent realizations upon outstanding debts prove to be more or less than estimated at the time of the creation of the existing reserve, the amount of the excess or inadequacy in the existing reserve shall be reflected in the determination of the reasonable addition necessary in the current taxable year.
(4) The computation of the addition to the reserve for bad debts.