Promo Codes and Discounts in Mobile App

Implementing Promo Codes and Discounts in Mobile Apps

Promo codes in mobile applications are three different mechanisms with different implementation complexity: native App Store/Google Play promo codes, custom server-side logic with your own codes, and promotional offers through RevenueCat/Adapty. Mixing them without understanding the limitations is a typical mistake.

Native App Store promo codes

Apple allows generating up to 1000 promo codes per app version (for paid apps) or IAP. User enters the code in App Store → gets the product. This comes to the app as a regular transaction — handled by standard StoreKit flow.

Problem: App Store promo codes cannot be applied inside the app. User must be redirected to App Store. For most monetization scenarios (discount for a specific user, referral program) this doesn't work.

Custom promo codes — server-side implementation

Custom promo codes live entirely on the backend:

Data schema:

promo_codes: id, code, discount_type (percent|fixed|trial_days), value,
             max_uses, used_count, expires_at, product_ids[], user_id (optional)
promo_redemptions: id, code_id, user_id, created_at, purchase_id

Client flow:

1. User enters code → client calls POST /api/promo/validate with code and product_id
2. Server returns discount type and applicable price
3. Client shows final price
4. Purchase through native IAP at full price → on server after transaction verification we apply the discount (credit the difference with currency, extend trial, etc.)

Direct price change for IAP on the client is impossible — Apple and Google don't allow dynamically changing product cost. All discount logic is implemented post-purchase on the server or through separate products with already reduced price.

Promotional offers as discount mechanism

For subscriptions on iOS — SKPaymentDiscount / SubscriptionOffer in StoreKit 2. Create an offer in App Store Connect with the desired price, server generates a signature for a specific user. This is a legal way to offer a discount without bypassing native billing.

// Get offer from server
let offerSignature = await serverAPI.getPromoSignature(userID: user.id, offerID: "discount_50")

let product = try await Product.products(for: ["premium_monthly"]).first!
let purchaseOption = product.subscriptionOffer(
    offerID: "discount_50",
    keyID: offerSignature.keyID,
    nonce: offerSignature.nonce,
    signature: offerSignature.signature,
    timestamp: offerSignature.timestamp
)
let result = try await product.purchase(options: [purchaseOption!])

Promo code input in UI

Promo code input field — separate screen or bottom sheet with debounce validation (request to server 300ms after last character). Important: show loading during validation and handle errors — "code expired", "code already used", "not applicable to selected product".

Estimated time — 2–3 days: server promo code model, validation and application API, UI component, integration with IAP flow.