Generation-Skipping Transfer Tax Amendments Act of 1999

Generation-Skipping Transfer Tax Amendments Act of 1999 - Amends Internal Revenue Code provisions concerning the special rules for allocation of the generation-skipping tax (GST) exemption to provide, as a general rule, that: (1) if any individual makes an indirect skip during such individual's lifetime, any unused portion of such individual's GST exemption shall be allocated to the property transferred to the extent necessary to make the inclusion ratio for such property zero; and (2) if the amount of the indirect skip exceeds such unused portion, the entire unused portion shall be allocated to the property transferred.

Requires the trusts resulting from a qualified severance to be treated as separate trusts.

Revises valuation rules concerning gifts for which a gift tax return was filed or a deemed allocation was made.

Requires regulations permitting the granting of extensions of time to make an allocation of a GST exemption.