26 C.F.R. § 25.6019-2
Except as otherwise provided in this section, the provisions of § 25.6019-1 (other than paragraph (d) of § 25.6019-1 ) apply with respect to the filing of a gift tax return or returns in the case of a husband and wife who consent (see § 25.2513-1 ) to the application of section 2513. If both spouses are (without regard to the provisions of section 2513) required under the provisions of § 25.6019-1 to file returns, returns must be filed by both spouses. If only one of the consenting spouses is (without regard to the provisions of section 2513) required under § 25.6019-1 to file a return, a return must be filed by that spouse. In the latter case if, after giving effect to the provisions of section 2513, the other spouse is considered to have made a gift not excluded from the total amount of such other spouse's gifts for the taxable year by reason of section 2503 (b) or (e) (relating, respectively, to certain gifts of $10,000 per donee and the exclusion for certain educational or medical expenses), a return must also be filed by such other spouse. Thus, if during a calendar year beginning after December 31, 1981, the first spouse made a gift of $18,000 to a child (the gift not being either a future interest in property or an amount excluded under section 2503(e)) and the other spouse made no gifts, only the first spouse is required to file a return for that calendar year. However, if the other spouse had made a gift in excess of $2,000 to the same child during the same calendar year or if the gift made by the first spouse had amounted to $21,000, each spouse would be required to file a return if the consent is signified as provided in section 2513.
26 C.F.R. §25.6019-2