How is a deferred compensation plan (under section 409A of the tax code) distribution taxed if leaving a job (but not retiring) and elected lump sum distribution?

I’m looking at a job opportunity that has a deferred compensation plan that complies with section 409A of the tax code. I’m wondering if I got this job, worked there for a few years, and then voluntarily left the job how much of the distribution would I lose to taxes, given that I elected to have it distributed in a lump sum upon separation of service?