What is the best way to process payment in an iOS app to allow a user to post an advertisement?

Regarding Apple app store you are in a gray zone. Apple does allow using external IAP for external services (doesn't have to be Physical goods) And your product sounds like a service, the question is - is it external or a content that is viewed / consumed in the phone? I think that for your case Apple will not allow using external IAP. Android is a bit more loose, but also there its kind of a gray zone. In a web site you can do whatever you want. You need to present that the service you sell is also used externally to the phone. Maybe buy credits for ADs and those credits can be presented as something that can be used outside of the phone or app that used to buy it. (Its very hard to convince Apple in this respect) Also ,maybe the way for you to get away of iOS/Android IAP is for you to make the payment only in your web site, (you can make this mobile friendly). You can enable other services and content in a native app. You can direct your app to your web site embedded in the app. Again Apple here are very strict, if you direct the app to a website (embedded in the app) only for purchase checkout they will reject it as well, but if you redirect your users to your web site for other stuff and one of them is payment, then maybe it will go OK with Apple. As I said Gray zone

Have you considered introducing a credits or points system similar to a virtual currency?  Bundles of points can be purchased through iTunes on iOS and if the same billing price points are used across web, mobile web and Android you have created a universal payment method for charging users.  All you then need to do is set price points for different value added service e.g. posting advertisements.

Well, Apple's policies w.r.t actions in such cases are pretty contradictory (considering what others have said here that Apple would probably reject the App) - since Apple shouldn't reject this App on in-App grounds since the content of the service is being used not only on iPhone but also on Android and Web; moreover the purchase for the same service (posting advertisement) is not restricted to only iPhone but to Android and Web as well - hence, based on their in-App definition this service should not be compelled to use the IAP mechanism. But again, as others have said they could reject if you put a web view only for the purchase thing. So 2 broad options I suggest you here - Option 1 - As already mentioned by someone here, add more web views to the app; doing few other functions besides purchase, for example - you can take profile settings to the web view, account info to the webview etc. Option 2 - Try to use this flow: 1. Forget about purchase via iPhone at first. 2. Let the user create and submit the App; but keep it un-published, and 3. Send a unique link to activate the add to poster's email, which will take the user to a web based standard payment processing, where use can pay the amount and as soon as the gateway realizes the payment and sends notification to the system; the user will get another notification that "Your Ad is now live, with its unique Ad ID etc; and you can view that on iPhone/ Android etc. This flow is good for the moderation purpose as well, if you'd want to include the same in this Ad posting process (to avoid profanity, malicious content etc and that shall make users more confident on your service too, that you moderate). Feel free to contact me for any further discussion on this matter via , we are third party App developers and consultants and can assist you well. Best -Sudeep http://www.agicent.com