One state, twenty-one separate Medicare plan markets.

Why "what is good in New Jersey" is the wrong question

Medicare Advantage and Part D service areas are approved county by county. New Jersey’s 21 counties therefore behave as 21 different sets of options, and they are not evenly sized — a dense northern county and a rural southern one can look very different from each other.

The parts of Medicare that are federal do not vary at all. Your Initial Enrollment Period is the seven months around your 65th birthday everywhere in the state. The Annual Enrollment Period is October 15 to December 7 everywhere. Late enrollment penalties for Part B and Part D are federal and permanent once they start. None of that is a New Jersey question.

What is a New Jersey question is which plans exist where you live, which providers are in them, and how your drug list is treated. Those are county-level and contract-year-level, which is exactly why I do not publish plan lists here — a stale list is worse than none.

Medigap in New Jersey runs on the federal clock

New Jersey does not add its own Medigap enrollment rules on top of the federal ones. In practice that means the six-month Medigap Open Enrollment Period that starts when you are 65 or older and enrolled in Part B is the window that matters most here, because during it you cannot be turned down or surcharged for health reasons.

This is a meaningful difference from New York, immediately next door, which requires Medigap to be sold on a continuous guaranteed-issue basis. If you are comparing notes with family across the Hudson, you are not comparing the same rules. That is worth knowing before you assume you can switch later on the same terms.

Retiring, downsizing, or moving within the state

A permanent move that takes you out of your current plan’s service area opens a Special Enrollment Period. Inside New Jersey, that usually means a move across a county line rather than a move across town.

The window’s timing depends on when you notify your plan relative to the move, so it is better raised early. If you are downsizing, moving closer to adult children, or splitting time between two homes, the address you are actually a permanent resident of is the one that drives your options.