(a) In general. A determination may take the form of a final disposition of a claim for refund. Such disposition may result in a determination with respect to two classes of items, i.e., items included by the taxpayer in a claim for refund and items applied by the Commissioner to offset the alleged overpayment. The time at which a disposition in respect of a particular item becomes final may depend not only upon what action is taken with respect to that item but also upon whether the claim for refund is allowed or disallowed.

(b) Items with respect to which the taxpayer's claim is allowed. (1) The disposition with respect to an item as to which the taxpayer's contention in the claim for refund is sustained becomes final on the date of allowance of the refund or credit if:

(i) The taxpayer's claim for refund is unqualifiedly allowed; or

(ii) The taxpayer's contention with respect to an item is sustained and with respect to other items is denied, so that the net result is an allowance of refund or credit; or

(iii) The taxpayer's contention with respect to an item is sustained, but the Commissioner applies other items to offset the amount of the alleged overpayment and the items so applied do not completely offset such amount but merely reduce it so that the net result is an allowance of refund or credit.

(2) If the taxpayer's contention in the claim for refund with respect to an item is sustained but the Commissioner applies other items to offset the amount of the alleged overpayment so that the net result is a disallowance of the claim for refund, the date of mailing, by registered mail, of the notice of disallowance (see section 6532) is the date of the final disposition as to the item with respect to which the taxpayer's contention is sustained.

(c) Items with respect to which the taxpayer's claim is disallowed. The disposition with respect to an item as to which the taxpayer's contention in the claim for refund is denied becomes final upon the expiration of the time allowed by section 6532 for instituting suit on the claim for refund, unless the suit is instituted prior to the expiration of such period, if:

(1) The taxpayer's claim for refund is unqualifiedly disallowed; or

(2) The taxpayer's contention with respect to an item is denied and with respect to other items is sustained so that the net result is an allowance of refund or credit; or

(3) The taxpayer's contention with respect to an item is sustained in part and denied in part. For example, assume that the taxpayer claimed a deductible loss of $10,000 and a consequent overpayment of $2,500 and the Commissioner concedes that a deductible loss was sustained, but only in the amount of $5,000. The disposition of the claim for refund with respect to the allowance of the $5,000 and the disallowance of the remaining $5,000 becomes final upon the expiration of the time for instituting suit on the claim for refund unless suit is instituted prior to the expiration of such period.

(d) Items applied by the Commissioner in reduction of the refund or credit. If the Commissioner applies an item in reduction of the overpayment alleged in the claim for refund, and the net result is an allowance of refund or credit, the disposition with respect to the item so applied by the Commissioner becomes final upon the expiration of the time allowed by section 6532 for instituting suit on the claim for refund, unless suit is instituted prior to the expiration of such period. If such application of the item results in the assertion of a deficiency, such action does not constitute a final disposition of a claim for refund within the meaning of § 1.1313(a)-3, but subsequent action taken with respect to such deficiency may result in a determination under §§ 1.1313(a)-1, 1.1313(a)-2, or 1.1313(a)-4.

(e) Elimination of waiting period. The necessity of waiting for the expiration of the 2-year period of limitations provided in section 6532 may be avoided in such cases as are described in paragraph (c) or (d) of this section by the use of a closing agreement (see § 1.1313(a)-2) or agreement under § 1.1313(a)-4 to effect a determination.