Notwithstanding the foregoing, for any subsequent taxable year of the service provider, the grandfathered amount may increase to equal the present value of the benefit the service provider actually becomes entitled to, in the form and at the time actually paid, determined under the terms of the plan (including applicable limits under the Internal Revenue Code), as in effect on October 3, 2004, without regard to any further services rendered by the service provider after December 31, 2004, or any other events affecting the amount of or the entitlement to benefits (other than a participant election with respect to the time or form of an available benefit). For purposes of calculating the present value of a benefit under this paragraph (a)(3)(i), reasonable actuarial assumptions and methods must be used. Whether assumptions and methods are reasonable for this purpose is determined as of each date the benefit is valued for purposes of determining the grandfathered benefit, provided that any reasonable actuarial assumptions and methods that were used by the service recipient with respect to such benefit as of December 31, 2004, will continue to be treated as reasonable assumptions and methods for purposes of calculating the grandfathered benefit.
Actuarial assumptions and methods will be presumed reasonable if they are the same as those used to value benefits under a qualified plan sponsored by the service recipient the benefits under which are part of the benefit formula under, or otherwise impact the amount of benefits under, the nonaccount balance nonqualified deferred compensation plan.
26 C.F.R. §1.409A-6