26 CFR § 25.2513-4 — Joint and several liability for tax.

If consent to the application of the provisions of section 2513 is signified as provided in § 25.2513-2, and not revoked as provided in § 25.2513-3, the liability with respect to the entire gift tax of each spouse for such “calendar period” (as defined in § 25.2502-1(c)(1)) is joint and several. See paragraph (d) of § 25.2511-1.