Here’s a practical, step-by-step guide to choosing the right payment gateway for your online store — quick checklist up front, then how to evaluate providers and what to test before you commit.

Quick checklist (start here)

• Know your needs: expected monthly volume, average order value (AOV), countries/currencies you’ll sell to, and whether you need subscriptions, marketplaces, or in-person POS.
• Compare costs: transaction % + per-transaction fixed fee, monthly fees, chargeback fees, cross‑border/currency conversion fees, and refund behavior. (Small differences compound with volume.) (shopify.com, forbes.com)
• Decide integration type: hosted checkout (fast, lower PCI burden) vs embedded/API integration (full branding, more control, usually lower rates at scale). (docs.stripe.com, decta.com)
• Verify security & compliance: confirm PCI DSS responsibilities and whether the gateway reduces your PCI scope (SAQ type, P2PE/tokenization). (pcisecuritystandards.org)
• Check payment methods: cards, Apple/Google Pay, BNPL (Klarna/Afterpay), local wallets for target markets. (techradar.com)
• Test UX and settlement: checkout flow on mobile, fraud/chargeback handling, and settlement timing to your bank. (shopify.com)

How to evaluate providers (detailed)

1. Pricing and total-cost projection

   • Don’t just compare the headline card % and fixed fee — include monthly fees, gateway fees, chargeback fees, cross‑border and currency markup, refund behavior, and any hardware/reader costs. Use your expected monthly volume and AOV to model annual cost for each provider. (Shopify and others give good checklists for what to include.) (shopify.com)

2. Integration & developer tools

   • Hosted/Checkout solutions (e.g., Stripe Checkout, PayPal Checkout) are fastest to launch and reduce your PCI scope because card data doesn’t touch your servers. API/Elements give full control and better conversion/branding but increase PCI responsibilities. Review each provider’s docs and sandbox — good docs + SDKs speed development and reduce bugs. (docs.stripe.com, stripe.com)

3. Security & compliance

   • Confirm the provider’s PCI DSS posture and whether they provide an AOC or P2PE/tokenization. Even with hosted checkout, you may still have SAQ obligations depending on how your site integrates scripts — verify which SAQ you’ll need. PCI SSC is the authoritative source. (pcisecuritystandards.org, reflectiz.com)

4. Supported payment methods & international reach

   • If you sell internationally, check supported currencies, cross‑border fees, local payment methods (e.g., SEPA, iDEAL, Alipay), and whether the gateway supports dynamic currency conversion or multi-currency pricing. Big global processors (Stripe, Adyen, PayPal) support many methods. (techradar.com, forbes.com)

5. Fraud tools & chargeback handling

   • Look for built-in fraud detection, 3‑D Secure support, dispute management tooling, and whether the provider offers chargeback representment or insurance. Chargebacks can be a significant operational cost. (techradar.com)

6. Payout timing, reserves, and underwriting

   • Check settlement windows (daily, 2–7 days), whether the provider holds reserves for new/at-risk accounts, and any rolling reserves or rolling reserve policies that could affect cash flow. Reviews and terms will show real-world behavior. (nerdwallet.com, techradar.com)

7. Reporting, refunds, accounting integration

   • Does it export transactions to QuickBooks / Xero / your ERP? Are reporting dashboards good enough for reconciliation and tax reporting? Good integrations save hours of manual work. (techradar.com)

8. Support, SLA and reliability

   • Look for 24/7 support options, merchant reviews, and SLAs. If payments go down, every minute costs you sales — reliability matters. (shopify.com)

Provider fit by business type (common patterns)

• No dev resources / very small / quick start: PayPal, Square, Shopify Payments (if on Shopify) — quick to set up, simpler UX but sometimes higher fees. (forbes.com, techradar.com)
• Developer-first / custom checkout / subscriptions / global: Stripe, Braintree, Adyen — flexible APIs, strong subscription tooling and multi-currency support; better for scaling. (docs.stripe.com, techradar.com)
• High-volume or enterprise: negotiate interchange-plus pricing with merchant account providers (or platforms like Adyen, Worldpay) to reduce effective cost at scale. (techradar.com)

Practical step-by-step selection process

1. Document requirements: list must-have payment methods, countries, subscription needs, POS needs, and projected volume.
2. Shortlist 3–5 providers who meet the feature set.
3. Model costs: compute annual fees using your projections (include chargebacks, refunds, cross-border). (shopify.com)
4. Sandbox and A/B test checkout flows (mobile & desktop) to measure conversion impact. (stripe.com)
5. Check legal terms: termination fees, rolling reserves, and dispute/chargeback policies.
6. Ask for references or reviews from merchants similar to you.
7. Start with a pilot (low risk) and monitor realtime reports for fraud, settlements, and disputes.

A few red flags to watch for

• Hidden monthly fees not shown on pricing pages.
• Long reserve periods or opaque underwriting for new accounts.
• Poor or slow support, especially around disputes.
• No clear PCI documentation or you’re asked to “just trust us” about compliance. (shopify.com, pcisecuritystandards.org)

Resources to compare providers and get current pricing

• Shopify’s payments/processor guide and checklist. (shopify.com)
• Vendor comparison articles (Forbes, NerdWallet, TechRadar) for feature/price snapshots (helpful but always confirm current pricing directly with the provider). (forbes.com, techradar.com)
• PCI Security Standards Council for compliance requirements. (pcisecuritystandards.org)

If you want, I can:

• Build a simple cost model (you give monthly volume + AOV + % international) comparing 3 gateways; or
• Shortlist 3 gateways tailored to your platform (Shopify / WooCommerce / custom) and needs (subscriptions, global sales, low dev resources).

Which would be more helpful: a cost model for your exact numbers, or a shortlist for your store type?