iPhones with aftermarket batteries installed by third-party repair shops are now eligible for service at Genius Bars and Apple Authorized Service Providers, according to an internal Apple document obtained by MacRumors from three reliable sources. The change was first reported by French blog iGeneration.

iPhone X battery with pull tabs via iFixit

This is significant news for ‌iPhone‌ repairs, as the Genius Bar and AASPs were previously instructed to deny service of any kind for an ‌iPhone‌ with a third-party battery, regardless of the circumstances.

If the repair is unrelated to the battery, the Genius Bar and AASPs are now instructed to ignore the third-party battery and proceed with service as normal, according to Apple's internal document. This could include repairs to the display, logic board, microphones, and so forth, with normal fees applying.

If the repair is related to the battery itself, the Genius Bar and AASPs are now permitted to replace the third-party battery with an official Apple battery for the standard fee. Before starting the repair, the Genius Bar must drain the third-party battery to less than 60 percent of a charge.

In the event Apple cannot safely remove a third-party battery due to broken or missing battery tabs or excessive adhesive, the customer is entitled to an ‌iPhone‌ replacement at the standard whole-unit out-of-warranty price.

The updated guidelines went into effect Thursday and should apply worldwide. Apple will still decline service for iPhones with third-party logic boards, enclosures, microphones, Lightning connectors, headphone jacks, volume and sleep/wake buttons, TrueDepth sensor arrays, and certain other components.

iFixit's director of communications Kay-Kay Clapp:

This decision proves that now, more than ever, the third-party repair ecosystem is an integral part of maintaining Apple's high-quality customer experience. If Apple is getting enough third-party repaired phones for a policy change, they clearly don't have the reach or capacity to maintain all the iPhones that they've sold. All of us, including Apple, benefit from the service provided by the repair community.

Apple similarly loosened its repair policy for iPhones with third-party displays back in February 2017.

Updated on March 7 with minor correction about whole-unit replacement fee.