Determining eligibility for introductory offer

eligibility.swift

func isEligibleForIntroductory(callback: @escaping (Bool) -> Void){
        
        guard let receiptUrl = Bundle.main.appStoreReceiptURL else {
            callback(true)
            return
        }
        
        #if DEBUG
            let urlString = "https://sandbox.itunes.apple.com/verifyReceipt"
        #else 
            let urlString = "https://buy.itunes.apple.com/verifyReceipt"
        #endif
        
        let receiptData = try? Data(contentsOf: receiptUrl).base64EncodedString()
        
        let shared_secret = "YOUR_SHARED_SECRET"
        
        let requestData = ["receipt-data" : receiptData ?? "", "password" : shared_secret, "exclude-old-transactions" : false] as [String : Any]
        var request = URLRequest(url: URL(string: urlString)!)
        request.httpMethod = "POST"
        request.setValue("Application/json", forHTTPHeaderField: "Content-Type")
        let httpBody = try? JSONSerialization.data(withJSONObject: requestData, options: [])
        request.httpBody = httpBody
        
        URLSession.shared.dataTask(with: request)  { (data, response, error) in
            guard let data = data, let json = try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String : AnyHashable], let receipts_array = json["latest_receipt_info"] as? [[String : AnyHashable]] else {
                callback(true)
                return
            }
            var latestExpiresDate = Date(timeIntervalSince1970: 0)
            let formatter = DateFormatter()
            for receipt in receipts_array {
                let used_trial : Bool = receipt["is_trial_period"] as? Bool ?? false || (receipt["is_trial_period"] as? NSString)?.boolValue ?? false
                let used_intro : Bool = receipt["is_in_intro_offer_period"] as? Bool ?? false || (receipt["is_in_intro_offer_period"] as? NSString)?.boolValue ?? false
                if used_trial || used_intro {
                    callback(false)
                    return
                }
                formatter.dateFormat = "yyyy-MM-dd HH:mm:ss VV"
                if let expiresDateString = receipt["expires_date"] as? String, let date = formatter.date(from: expiresDateString) {
                    if date > latestExpiresDate {
                        latestExpiresDate = date
                    }
                }
            }
            if latestExpiresDate > Date() {
                callback(false)
            } else {
                callback(true)
            }    
        }.resume()   
    }

@linktoshubham - in the Sandbox it seems like receipts are no present until a purchase is made, but in production after an app is installed there should be a receipt. As you saw, calling SKReceiptRefreshRequest prompts for a user password, so generally do not use that unless you are at a point where the user was prompted for an iTunes password already. If there is no receipt, you just have to assume the user is not valid for an introductory offer and display the normal price - if the offer actually applied to them, they would be charged the offer price instead. But, as I said there should be a receipt normally before any purchase is made.