what payment api should I use for a saas subscription app?

For a SaaS subscription app, the best default choice is usually Stripe Billing.

Why Stripe is the most common pick

• Strong subscription support: recurring billing, trials, coupons, proration, upgrades/downgrades
• Good developer experience: clean APIs, webhooks, lots of SDKs
• Handles tax/VAT options, invoices, and receipts
• Good customer portal for updating cards, canceling, etc.
• Works well for global SaaS businesses

Good alternatives

• Paddle: great if you want more of a Merchant of Record model so they handle taxes/VAT/sales tax for you. Very useful for international SaaS, especially digital products.
• Chargebee: good if you need more advanced subscription management on top of Stripe or other processors.
• Braintree: solid payments platform, but less common for SaaS subscriptions than Stripe.
• PayPal: useful as an additional payment option, but usually not the primary subscription system.
• Adyen: strong enterprise/global option, better for larger companies.

Quick recommendation by situation

• Early-stage SaaS / startup: Stripe
• Want taxes handled for you: Paddle
• Complex billing at scale: Chargebee + Stripe or Adyen
• Enterprise/global payments: Adyen or Stripe

My practical suggestion

If you’re building a new SaaS app and want the simplest path:

1. Use Stripe Billing
2. Add Stripe Checkout or Payment Element
3. Use webhooks for subscription state changes
4. Add a tax solution later if needed

If you want, I can also recommend the best option based on:

• your country
• whether you sell B2B or B2C
• whether you need global tax handling
• your tech stack (Next.js, Django, Laravel, etc.)