iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone SE, released on 2016-03-31T16:55:26Z. The update package is 35 MB. This is a delta (partial) update that requires 9.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 23f452652f414ab6f01f2c4321ec1746ad2843c4.zip.