If you replace the battery in the newest iPhones, a message indicating you need to service your battery appears:
- Settings > Battery, next to Battery Health.
The "Service" message is normally an indication that the battery is degraded and needs to be replaced. The message still shows up when you put in a brand new battery.
If you see this message, the battery in your iPhone cannot be verified and reported battery health information isn't available. This might be due to the installation of a battery that is not a genuine battery.
This message applies to iPhone XS, iPhone XS Max, iPhone XR, and later. Indeed Apple does not validate anymore third party battery replacement. This doesn't mean your battery as an issue but it was replaced with a compatible battery that can work as good as an original one.
Also, we've confirmed that this doesn't throttle the iPhone's performance on a healthy battery, for example. But you won't be able to easily see your battery's health and know when it's time to replace it.
Fortunately, your replacement battery will continue to work perfectly fine, and you'll get all of the benefits that come with a new battery.
If you want to learn more about it.