As the government reaches for more revenue to avert the fiscal cliff, new limits on tax expenditures currently under discussion could have the effect of reducing potential 401(k) contributions by 65 percent.

That conclusion is a matter of arithmetic, though the numbers vary with a person's income, according to Brett Goldstein, director of retirement planning for American Investment Planners, a Jericho, N.Y., financial advisory firm.

Under a proposal dubbed the 20-20 cap now under consideration, employees would be able to contribute the lesser of $20,000 or 20 percent of their pay, Goldstein told AdvisorOne in an interview.