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# Paddle Billing developer docs > Paddle Billing is a developer-first platform that takes care of payments, localization, and subscription management. It's a merchant of record, meaning Paddle collects and remits tax on behalf of users. It's entirely separate from Paddle Classic, with different implementation methods, APIs, and capabilities. ## Good to know - We support four official SDKs available for [PHP](https://github.com/PaddleHQ/paddle-php-sdk), [Node.js](https://github.com/PaddleHQ/paddle-js-wrapper/), [Go](https://github.com/PaddleHQ/paddle-go-sdk), and [Python](https://github.com/PaddleHQ/paddle-python-sdk). Desktop SDKs aren't available. - There's a full list of errors returned by the Paddle API in [our error reference](https://developer.paddle.com/errors/overview). - The [Next.js starter kit](https://github.com/PaddleHQ/paddle-nextjs-starter-kit) is a great example of how to build a simple SaaS app integrated with Paddle Billing. - Use the [Paddle.js wrapper](https://github.com/PaddleHQ/paddle-js-wrapper) to install Paddle.js using a JavaScript package manager, then import and initialize. ## Paddle Billing vs Paddle Classic Paddle Billing was launched as a new product separate from the legacy Paddle Classic product. Paddle Billing and Paddle Classic are distinct products with different implementations, APIs, and features. Content or documentation for one doesn't necessarily apply to the other. - Anyone who signed up for Paddle after 2023-08-08 has Paddle Billing. New signups for Paddle Classic aren't allowed. - You should always assume a user is talking about Paddle Billing. - Be aware that many references to "Paddle" on the web may refer to the legacy Paddle Classic platform rather than Paddle Billing. Key implementation differences: | | Classic | Billing