SaaS Billing Guide SaaS Payment Gateway: How to Choose One
Confused by payment gateways that only authorize cards? Compare what each one really handles—billing, retries, proration—before you pick on fees alone.
Daniel R. Whitfield 8 min read
Here's the thing nobody tells you upfront: a "payment gateway" is a badly overloaded term. Strictly speaking it's the pipe that authorizes a card charge and returns a yes or a no. But for a subscription business it also has to remember your customers, chase their expired cards, and quietly fix a failed renewal at 3am while you're asleep. Those are three different jobs. Plenty of providers only do the first one.
So before you start comparing quotes, decide which jobs you're actually buying. That single question will save you more money than any negotiation on rates.
Most founders pick on transaction fees. It's the only number that's easy to compare, so it wins by default. Then six months later they're paying an engineer to hand-build retry logic and a finance person is issuing manual credits for plan changes the system couldn't prorate. The cheap gateway wasn't cheap. It just moved the cost somewhere harder to see.
Four layers people keep collapsing into one
A gateway is one component in a stack. Mix up the layers and you'll compare apples to invoices.
- Gateway. Routes the transaction, gets the authorization, tells you what happened.
- Merchant account (the acquirer). Holds funds and carries settlement risk. Different beast entirely.
- Processor. The plumbing between the gateway and the card networks and banks.
- Billing layer. Plans, invoices, proration, dunning, tax. Sometimes bundled. Often not.
In reality the lines smudge. Stripe, for instance, bundles gateway, merchant account and subscription billing into one account, which is precisely why nobody says "I'm choosing a payments platform" — they say "I'm choosing a gateway." Fine. Just know what's in the box before you sign, because the gaps are where the expense hides.
What recurring revenue actually demands
Taking a one-off payment and billing someone every month are not the same problem wearing different hats. Subscriptions need state. They need memory. An ecommerce checkout can forget you the moment the charge clears; a subscription gateway can't.
Stored cards, and the card-update problem
You'll want tokenization — the provider holds the sensitive card data and hands you a token you can charge against later. That's table stakes. The interesting question is what happens when a card expires. Card networks run update services that push fresh card details to providers automatically. Ask whether yours is wired into them. If it isn't, you'll be emailing customers for new card numbers one by one, and a chunk of them will simply never reply.
Retries and dunning: where the money leaks
Involuntary churn — the failed renewal, the maxed-out card, the bank's fraud filter eating a legitimate charge — quietly bleeds SaaS revenue every single month. Can you set your own retry schedule? Trigger reminder emails? Put an account into a grace period instead of cutting access the instant a charge bounces? And the real tell: does the provider handle any of this for you, or are you writing that state machine yourself?
Upgrades, downgrades, trials
Your customers move between plans constantly. Mid-cycle upgrades need proration. Trial-to-paid conversions need to happen without a workaround duct-taped on. If the platform can't do it natively, your finance team becomes the proration engine, one manual credit at a time. That doesn't scale and it's miserable work.
Can you reconcile payouts to MRR?
You need to tie gateway payouts back to your revenue numbers, and that means seeing fees separated from gross charges and getting a clean export into your accounting system. Ask what the reporting looks like before you commit. Monthly reconciliation that takes three days isn't a reporting feature, it's a tax on your finance team.
Comparing options without drowning
Work through these in order. Each one shrinks the shortlist, so by the end you're choosing between two or three rather than twenty.
1. Write down what you actually sell
Flat monthly? Per seat? Metered or usage-based? Annual contracts? Multi-currency pricing? Be honest and thorough here. Your gateway has to handle your most complicated plan, not your simplest one — and usage-based billing in particular is where basic gateways fall over. If you sell metered plans, test that path first.
2. Where are your customers?
Selling globally means you need local payment methods and someone who understands currency conversion and tax obligations in the customer's country. Those rules vary by jurisdiction, sometimes wildly, so confirm them against the provider's official documentation and run the tax questions past your adviser. There's a practical angle too: settling in the currency your customer actually uses cuts friction and cuts failed charges.
3. Do the fee math properly
Fees stack. Percentage per transaction, a fixed fee per charge, a currency conversion spread, chargeback fees, a monthly account fee. Rates swing by country, card type and volume, so the provider's published pricing page is the only source you should trust. Take your real monthly volume and run it through the actual rate card — don't just assume a headline percentage applies to you. Then add the costs the rate card doesn't show: failed-payment recovery, manual admin, engineering time.
4. How fast can you go live, and who's doing the work?
Look for API docs you can actually read, a sandbox to test in, webhooks for payment events, and a hosted checkout if building a card form from scratch sounds like a waste of your quarter. One thing people forget: a beautiful developer API is worthless if your finance team can't issue a refund or edit an invoice without filing a ticket. Check both sides of the house.
5. Support and uptime
Payments break at the worst possible moment. It's practically a law. So ask about uptime commitments, whether support covers your time zone, and whether you get a named human to call. A slightly higher rate from a provider that answers the phone at 2am is frequently the smarter purchase.
6. The contract, read slowly
Notice period. Early-termination terms. Chargeback thresholds that could get your account frozen. And the one everyone skips: can you export stored tokens and customer data if you walk away? Data portability only matters the day you need it, and by then it's too late to negotiate.
Two options, side by side
The numbers below are made up — illustrative only, not any real provider's pricing. The point is the shape of the comparison: a SaaS doing $80,000 a month across roughly 2,000 subscriptions.
| Factor | Option A | Option B |
|---|---|---|
| Recurring billing | Built in: retries, proration, dunning | Gateway only; billing built in-house |
| Failed-payment recovery | Automatic retry schedule and reminders | Manual; needs engineering work |
| Effective monthly cost | Higher published rate, less admin time | Lower rate, plus build and upkeep |
| Go-live time | Days, with configuration | Weeks, with custom code |
Option A charges more per transaction and recovers failed renewals on its own. Option B looks like the bargain — until you price the engineering hours to build retries and proration, add the ongoing maintenance, and then subtract the renewals you never recovered. For most subscription businesses that last line dwarfs a few basis points on the rate.
Where teams go wrong
- Rate shopping in isolation. Retry, proration and reporting gaps cost more than the fees ever save.
- Assuming billing is included. Find out whether subscriptions, invoices and tax are in the box or need another tool bolted on.
- Never touching the sandbox. Before you commit, run a card failure, a mid-cycle upgrade and a trial conversion through it. Watch what happens.
- Discovering portability at the exit. Read the export terms before signing. Not after.
- Undercounting currencies. Map your biggest customer markets early, not after launch.
- Forgetting PCI scope. A hosted checkout or hosted fields usually shrinks what you're on the hook for. Confirm the specifics on the provider's official compliance documentation.
What I'd actually do
Before you talk to a single provider, write three things down: your billing model (the messy parts included), your top three customer countries, and your monthly volume. Those three lines do most of the filtering for you.
With that in hand, shortlist two or three providers that handle your most complex plan type and your biggest markets. Compare them on failed-payment recovery, proration, reporting, contract terms and total cost — counting your own engineering time, not just the headline rate. Then pick one and try to break it in the sandbox with a realistic failure scenario: expired card, insufficient funds, mid-cycle upgrade. Confirm fees, tax rules and compliance obligations on the provider's official pages before you sign anything.
Everything above is general information. It isn't financial, legal or tax advice.
