Third party payment gateeway instead of In-app purchase

Our application facilitates doctors in storing patient records, including essential documents and images. However, a subscription is required for users to store images on a monthly or yearly basis. Considering we also have an Android application, we're considering using the same payment gateway for both platforms. Is it acceptable to integrate a third-party payment gateway instead of relying on an in-app purchase system?

Thanks in advance.

Third party payment gateeway instead of In-app purchase
 
 
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