It's a phone that's previously been owned by someone else but has been thoroughly tested by our service engineers who perform a 51-point test to make sure all pre-owned nu phones run and look the way you expect them to. All our phones have at least 80% battery life (As of June 2022, the average battery capacity of nu certified phones is 92% Min. capacity is 80%) and only the best phones make the final cut to become nucertified. Want to see what we test? See here. This means you'll get a quality pre-owned phone at an awesome price. See our phones here.