How to take payments in your AI-built app

Use Stripe when you can be the seller and you will deal with sales tax. Use Paddle, Lemon Squeezy, or Polar when you want a merchant of record to collect the tax for a digital product. Their published starting fee is 5% + 50¢, against Stripe's 2.9% + 30¢ for a domestic card. The gap is the tax and the paperwork, not a better checkout button. Fees below were read from each company's pricing or fee docs on 2026-10-22.

The call

You can open a Stripe account, customers pay by card, and you will register for sales tax yourself: start with Stripe. No monthly fee on the standard pricing page. You are the merchant of record.
You are selling software or another digital product and you do not want to file VAT: start with Paddle if one rate and a monthly payout are enough. Start with Lemon Squeezy if you need a PayPal payout. Start with Polar if you want to choose when the money leaves, and your country is on Polar's Stripe Connect list.
You want Stripe's dashboard and you also want Stripe to be the seller: that product is Managed Payments, for eligible digital goods. The docs page checked here does not print a processing fee, so this guide does not invent one. Read the eligibility page before you plan on it.

A checkout button is not a secure app. Secret keys and the webhook signing secret stay off the frontend. The security checklist has the prompt. The app still needs a host that allows a commercial project: Vercel's free Hobby plan does not. That limit is in where to host.

Fees and who is the seller

Last checked 2026-10-22. Extra fees apply on top of the headline rate.
	Stripe	Lemon Squeezy	Paddle	Polar
You are the seller?	Yes, on ordinary Stripe products. Managed Payments is the exception: Stripe is the merchant of record for eligible digital products.	No. Lemon Squeezy says it is the merchant of record.	No. Paddle says it is the merchant of record.	No. Polar says it is the merchant of record.
Published starting fee	2.9% + 30¢ per successful domestic card charge. No setup fee and no monthly fee on standard pricing.	5% + 50¢ of the order total. No monthly ecommerce fee.	5% + 50¢ per checkout transaction. No monthly fee.	Starter is free, then 5% + 50¢. Pro is $20/month at 3.8% + 40¢. Growth is $100/month at 3.6% + 35¢. Scale is $400/month at 3.4% + 30¢.
Extra published fees	+0.5% for manually entered cards. +1.5% for international cards. +1% if currency conversion is required.	+1.5% outside the US. +1.5% for PayPal. +0.5% for subscription payments.	The pricing page says there is no extra charge for additional payment methods. Products under $10 can ask for a custom rate.	+1.5% for non-US cards. Current paid plans have no separate subscription surcharge. Disputes are $15. Organizations created before May 27, 2026 can stay on an older 4% + 40¢ rate, plus 0.5% on subscriptions.
Sales tax and VAT	Your job, unless you are on Managed Payments, which handles indirect tax in more than 80 countries. Stripe Tax is a separate product and does not, by itself, make Stripe the seller.	Lemon Squeezy calculates, collects, and files tax as the merchant of record.	Paddle calculates, collects, and remits tax as the merchant of record.	Polar takes on international sales-tax liability as the merchant of record.
Payouts	To the Stripe account. A business can open one only in a country on Stripe's global availability list, and can then sell worldwide.	Bank payouts in the countries on Lemon Squeezy's list, or PayPal in 200+ countries. US bank payouts are free. Banks outside the US cost 1% per payout. PayPal is $0.50 in the US, or 3% capped at $30 outside the US.	Monthly, once the balance is at least $100. Paddle lists payout currencies: AUD, CAD, CHF, CNY, CZK, DKK, EUR, GBP, HUF, PLN, SEK, USD, and ZAR. Local transfers in the matching country are typically free. A SWIFT transfer, when the currency does not match the bank's country, is $/€/£15.	You withdraw through Stripe Connect Express, to a bank in the same country as the account. USD minimum is $10. Stripe's payout fees, which Polar says it does not mark up: $2 in a month you pay out, plus 0.25% + $0.25 per payout. New organizations wait 7 days before a charge can be withdrawn.

What the percentages leave out

Merchant of record

The merchant of record is the seller the customer is buying from. That seller collects the tax, handles the chargeback, and appears on the receipt. Lemon Squeezy, Paddle, and Polar publish that they take this role. Ordinary Stripe does not: the comparison table in Stripe's Managed Payments docs says the merchant of record is "your business" for other Stripe products, and "Stripe" for Managed Payments. If you are in a country where registering for VAT is the part you cannot do yet, the 5% products are the ones whose docs say they file it.

Where you can get paid

Stripe's global availability page is the list of places a business can open Stripe. This guide does not turn that page into a count. Lemon Squeezy publishes a bank-payout country list that includes India, with a note that new Indian Stripe accounts are invite-only and those merchants use PayPal instead, plus PayPal payouts in 200+ countries. Paddle says it works for software businesses except a published unsupported list (that list includes Russia, Iran, North Korea, Cuba, and Venezuela) and pays in the currencies above. Polar's payout list is the Stripe Connect Express list and includes India, Nigeria, and Pakistan. The bank has to be in the same country as the Polar account.

Lemon Squeezy's fee page is still the 5% + 50¢ schedule. A post on January 28, 2026 says the team is building Stripe Managed Payments and that existing Lemon Squeezy users did not have to move. If you open a new store, read that post and the fee page together. Polar says its $20 Pro plan saves money against Starter once sales are about $1,379 a month. Below that, Starter is the cheaper published plan.

What to ask the AI tool to build

Stripe
Ask for Stripe Checkout or a Payment Link, a publishable key in the browser, and the secret key only in server code. Ask for a webhook that verifies Stripe-Signature with the raw body before it updates your database. Stripe's docs are what coding agents already imitate, which is why this is the path they scaffold, and why the secret ends up in the wrong file if you do not say otherwise.
Lemon Squeezy, Paddle, Polar
Ask for their hosted checkout and a webhook, not a card form you own. You still verify the webhook, and you still keep the API key on the server. You do less tax code. Bolt's Supabase docs mention edge functions as the place a payment call such as Stripe should live. The same idea holds for the other three: the secret stays in the function, not in the page.

Do not charge a second person until auth and the database rules are on. That work is the SaaS guide and the checklist, not a sentence in the checkout prompt.

Pick by situation

First paid test, US cards, you can file tax later. Stripe. Lowest published card rate. Add Stripe Tax or a merchant of record before the sales are outside one state or one country you understand.
Digital product, customers in several countries, you will not file VAT. Paddle if a monthly payout that waits until the balance is at least $100 works, and one of its payout currencies is how you want to be paid. Lemon Squeezy if you need PayPal. Polar if you want to withdraw from $10 in USD and your country is on its payout list.
You already crossed about $1,379 a month on Polar. Polar's own table says Pro at $20/month is the cheaper plan from there. Until then, the free Starter rate is the one to use.
The agent already pasted a Stripe snippet. Keep it only if the secret key and the webhook secret are server-only and the signature is checked. Otherwise you have a button, not a payment integration.

Questions people actually ask

Stripe, Lemon Squeezy, Paddle, or Polar: which should I use?

Use Stripe if you can open a Stripe account, you are fine being the seller, and you will handle sales tax yourself or with Stripe Tax. The published domestic card rate is 2.9% + 30¢, with no monthly fee on standard pricing. Use Paddle, Lemon Squeezy, or Polar if you want a merchant of record to collect and remit sales tax and VAT. All three publish a starting rate of 5% + 50¢. Pick Paddle when you want that rate without the extra international, PayPal, and subscription lines the others print. Pick Lemon Squeezy when you need PayPal payouts or a bank in their published country list. Pick Polar when you want to withdraw yourself through Stripe Connect Express, including from countries on Polar's payout list such as India, Nigeria, and Pakistan.

Who handles sales tax?

On ordinary Stripe products, your business is the merchant of record. Stripe Tax can help you calculate tax, and Stripe's Managed Payments product is a separate option where Stripe is the merchant of record for eligible digital goods. Lemon Squeezy, Paddle, and Polar each publish that they are the merchant of record and that they handle sales tax, VAT, and GST. That is the reason their percentage is higher than Stripe's card rate.

Can the AI tool set up checkout for me?

It can scaffold Stripe Checkout or a hosted checkout. The failure is a secret key in a VITE_ or NEXT_PUBLIC_ variable, or a webhook that marks an order paid without checking the signature. Keep the secret key and the whsec_ signing secret on the server. Run the security checklist before the first real charge. Hosted checkouts from Lemon Squeezy, Paddle, and Polar leave more of that machinery on their side.

Sources

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