One of the life events that can trigger payment under your NQDC plan. Section 409A defines disability to cover situations in which, at a minimum, you are unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment expected to result in death or to last for a continuous period of not less than 12 months; or in which you receive income replacement benefits for a period of not less than three months under a plan provided by your company. Your NQDC plan can use a more limited definition.