Polar review

Polar is a hosted billing platform and merchant-of-record service, not a billing library or a self-hosted server. It sits between a product and its customers: the product sends usage events, Polar aggregates them into meters, then combines metered charges with subscriptions or prepaid credits on invoices.

That makes it relevant to AI and other usage-based products where a seat-based subscription alone does not reflect customer consumption. Polar's event metering covers calls, tokens and GPU seconds; usage can be settled at the end of a billing cycle. Teams can attach inference costs to events and view revenue, cost and gross margin by customer.

As merchant of record, Polar says it handles payments, sales tax, fraud, refunds and chargebacks in more than 100 markets. The platform therefore reaches beyond invoice generation into payment and tax operations. It is a vendor-operated service: confirm its API, data handling and export options before making it a central dependency.

The homepage names a Python SDK and webhook infrastructure, and describes integrations with a Polar MCP server. Its HTTP MCP endpoint is https://mcp.polar.sh/mcp/polar-mcp; Claude Code, Cursor, ChatGPT and Claude Desktop are named clients. The MCP flow uses OAuth, with a browser sign-in rather than an API key pasted into an agent. Agents can query customer, usage and revenue data, and create products, discounts and refunds.

The homepage does not publish API protocol details or endpoint patterns. Confirm the API surface, supported SDK languages and webhook event coverage in Polar's docs before choosing an integration. The Python SDK is the only language-specific SDK named on the homepage. A code sample shows attaching an _cost amount and currency to events for margin reporting.

Polar describes a flow from event ingestion to live meters and automatic invoice settlement. That reduces the need to build usage aggregation and billing-cycle reconciliation yourself, but you still need to instrument events and validate how retries, duplicate events and failed webhooks are handled.

Starter costs $0 per month and charges 5% + $0.50 per transaction. Pro is $20 per month at 3.8% + $0.40; Growth is $100 per month at 3.6% + $0.35; Scale is $400 per month at 3.4% + $0.30. The Startup Program offers Scale free for 12 months to early-stage AI startups. Early Member is a grandfathered plan for organizations created before May 27, 2026, with a 4% + $0.40 transaction fee and a 0.5% fee on subscription payments.

The monthly plans list a 0% subscription fee, except Early Member. All plans add 1.5% for international cards. Active payouts cost $2 per month, plus 0.25% + $0.25 per payout; cross-border currency conversion adds 0.25% to 1%. Disputes cost $15 each. These charges can matter more than the monthly fee as transaction volume grows. The vendor doesn't publish annual prices or a free-tier transaction ceiling, so model your mix of payments and ask about limits before launch.

Polar's homepage has an Open Source link, but the vendor doesn't publish the billing service's licence or a self-hosting path there. The product described is a hosted service; do not assume you can run its billing infrastructure in your own environment. Ask Polar which components are open source, what licence applies and whether those components include the production billing service.

The vendor doesn't publish a data export process on its homepage. Before adopting Polar, confirm whether you can export customers, products, subscriptions, usage events, invoices and payment records in usable formats, and how long exports remain available after cancellation.

Migration effort will depend on how much billing state and product logic you place in Polar. Metered events and pricing configuration may need mapping to a replacement service, while payment and tax operations may need a separate provider. Keep your own copy of source usage events and document pricing rules to reduce that dependency.

Polar's live metering and end-of-cycle settlement are designed for products that need usage to flow into billing without manual reconciliation. Its customer-level cost insights can also help teams spot accounts whose inference costs exceed revenue. Those features make event correctness important: verify duplicate handling, retries, late events, corrections and invoice previews before connecting meters to customer charges.

The vendor doesn't publish rate limits, uptime commitments or detailed reliability targets on its homepage. Ask for those limits, incident procedures and support response terms for the plan you expect to use. The listed plans range from standard support on Starter to prioritized support on Pro and Growth, and P1 support plus a shared Slack channel on Scale.

Polar says it handles sales tax, fraud, refunds and chargebacks as merchant of record in more than 100 markets. Confirm eligible countries, product restrictions, payout timing and the responsibilities that remain with your company. The homepage says MCP access uses OAuth, but teams should also review access controls and data permissions before enabling billing actions for agents.