26 CFR § 26.2641-1 - Applicable rate of tax.

The rate of tax applicable to any GST (applicable rate) is determined by multiplying the maximum Federal estate tax rate in effect at the time of the GST by the inclusion ratio (as defined in § 26.2642–1). For this purpose, the maximum Federal estate tax rate is the maximum rate set forth under section 2001(c) (without regard to section 2001(c)(2)).