Workers over age 50 would no longer be able to make catch-up contributions on a pretax basis to their retirement plans under a new amendment to the GOP's Senate version of the tax bill.

Orrin G. Hatch, chairman of the Senate Finance Committee, filed the amendment to the bill on Monday.

The full text of the bill is here, and amendments are here.

This amendment would permit workers over age 50 to contribute up to an additional $9,000 each year to their retirement plans, but it would require that these contributions be made to Roth accounts. Those are accounts where taxes are paid upfront.

Currently, employees over age 50 can contribute up to $6,000 in additional savings each year to their 401(k) plan and do so on a pretax basis. That's on top of the current annual $18,000 limit.