In my APP for now contains IAP for one time purchase.
By adding to APP auto-renewable subscriptions can I ask from customers(that purchased on App Store and IAP ) to purchase subscription. For customers that purchase IAP, ask to purchase subscription after year from IAP was purchased.
It depends on what the IAP gave the customer.
If the IAP unlocked something and you're now going to lock it behind a subscription, then no, you shouldn't do that. You can't say to someone, "Pay me $5 and you get Feature A," then some time later say, "Actually, I'm taking away Feature A unless you pay me $5 every year".
If, however, the IAP gives a feature that is not going to be locked behind the new subscription, then you can create the new subscription and customers can decide if they want to buy it. Any customers who already bought the IAP should still retain the features it unlocked.
In general when doing this, you need to put new features into the subscription and leave previous IAPs as they are. You can remove them from sale so no one can buy them going forward, but anyone who already bought the IAP should retain those features going forward.
Or, you could offer previous IAP purchasers a discounted subscription price. So, two subscriptions, one for new customers who have not previously purchased the IAP, and one at a lower price taking into account what they previously paid for the IAP, e.g.:
- IAP: $5
- New sub: $10/year.
- New sub for IAP purchasers: $8/year.
You have to figure out what works best - but you definitely shouldn't annoy your existing customers, or you'll find out you don't have any.
