2 or more plans treated as single plan .—

If the amount of contributions on behalf of the employees allowed as a deduction under section 404 for the taxable year with respect to such plans, taken together, bears a uniform relationship to the compensation (within the meaning of section 414(s)) of such employees, the plans shall not be considered discriminatory merely because the rights of employees to, or derived from, the employer contributions under the separate plans do not become nonforfeitable at the same rate.

If the employees’ rights to benefits under the separate plans do not become nonforfeitable at the same rate, but the levels of benefits provided by the separate plans satisfy the requirements of regulations prescribed by the Secretary to take account of the differences in such rates, the plans shall not be considered discriminatory merely because of the difference in such rates.