> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hub2.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

The implementation of the HUB2 Payment API is a bit more challenging than the Transfer API, as an interaction with the end customer is required.

<Note>
  * [Link to the API reference for payments](/api-reference/payments)
  * [Link to the OpenAPI documentation](https://api.hub2.io/docs-json)
</Note>

## Payment lifecycle (asynchronous circuit)

This is a common way of how payments are handled by the HUB2 API - it may vary depending on scenarios and providers.

<Frame>
  <img src="https://mermaid.ink/img/pako:eNq9k1FPgzAUhf_KTV83ssTHJluybFNJdBKZb7xUehmN0GJ7O7Ms--92AhoXhz7ZF5rL13Mu59IDy41ExpnDV486x6USWyvqTENYjbCkctUITbCoFGpq6_do8zIUo9lsdOufrzgkD-kGJo3Y1wGKlKbwcC28NoRg1bYkMAV0eDxNVutlvL5pmVM1CmpRr8zBInmroZOMPxRjOezPz-i-oaFOpovH1XyzWv61EfkdHCXW7JREyyFFLXssnAp5Ohoy_jGB0ZfxGz6XxrxAE3SV3p59-oltZ8JBG1LFHsjATlRKiuDW9XGx2cRUVRAFR4J8l0__NvrK9RFdY7RDeFNUfoNb7zPV_7AHYyFO1kPJpk-LxSpNYQLX8_iun-2FH7GHVfE5vK7062Scz3N0LvgUQlUo2ZjVaGuhZLhRh9PxjFGJNWaMh63EQviKMpbpY0CFJ5Pudc44WY9j5ptTdN0FZLwQlcPjOzN5MOQ" />
</Frame>

## Payment lifecycle (synchronous circuit)

This way of processing payments is only available for the provider wave.
It allows merchants to receive redirection links without subscribing to a webhook and without doing polling.

<Warning>
  This circuit can only be activated on request to HUB2 Support. Please contact HUB2 Support for more information.
</Warning>

<Frame>
  <img src="https://mermaid.ink/img/pako:eNqNk19rwjAUxb_KJa9ahD0GFKR2W2Fzxbq3vsTm1oa1SZc_iojffalt3ZRN1peUyy8n557cHEmuOBJKDH46lDkuBNtqVmcS_NcwbUUuGiYthJVAabv6K-q89MVgNhs9u80DheQtXcOkYYfaQ4GQ1i-mg5fKImixLS2oAno8nibRchEvnzqmrQZeLRiUKWi0TkvoJeOzYszvn09v6MGQmZiDzO_YmYaraL6OFtduRolWO8FRU0hR8sGLt-azMn0WA3O238mt0DRKGoS9sCUYy6wz_-2T33N5ldklhNZpdzsUpLKiOIBVsGOV4Myr9Mrdpo67ae539Gdjo78bA6UhTpb3bKfvYRilKUzgcR6_DCn_MRcDLIpL3n3p5nK-I9zjplTqA4zLczTGn1MwUSEnY1KjrpngfsCP7faM2BJrzAj1vxwL5iqbkUyePMqcVakfE0Ktdjgmrmkz6d8DoQWrDJ6-AIT5DAI" />
</Frame>

**Note :**

* PI : Payment Intent - the payment intent
* P : Payment - the payment attempt