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

# Crypto Lending

> Earn yield on crypto assets through fixed-term and flexible lending plans with 13 API endpoints for full lifecycle management.

Earn yield on crypto assets through fixed-term and flexible lending plans -- 13 API endpoints for full lifecycle management.

## Capabilities

The Crypto Lending API supports two plan types with distinct yield mechanics.

* **Fixed plans** -- lock assets for 10-360 day terms. Interest paid at maturity. Interest ratio conversion when target currency differs from source currency.
* **Flexible plans** -- deposit and withdraw anytime. Interest calculated hourly, credited daily. Auto-reinvestment option compounds returns.
* **\~90 supported assets** -- invest in a wide range of crypto assets (check available plans dynamically via the plans endpoint)
* **Auto-invest** -- configure automatic recurring investments into Flex plans
* **Full lifecycle API** -- create, monitor, withdraw, and close investments programmatically

## Who Uses This

* **Yield integrators** -- fintechs and platforms offering lending products to end users via API. Fetch available plans, create investments on behalf of customers, track earnings.
* **Treasury operations** -- exchanges and trading firms putting idle [Main balance](/concepts/balances) assets to work in Flex plans between active trading periods.

## Common Integration Patterns

**Yield-as-a-service** -- Fetch available Flex plans via `POST /api/v4/main-account/smart-flex/plans`. Present plan options (asset, interest rate) to end users. Create investments via `POST /api/v4/main-account/smart-flex/investments/invest`. Track earnings through `POST /api/v4/main-account/smart-flex/investments/payment-history`. Enable auto-reinvestment for compounding.

**Idle asset management** -- Monitor [Main balance](/concepts/balances) for idle assets. Invest surplus into Flex plans (withdraw anytime, no lock-up). Set up auto-invest for recurring allocation. Withdraw back to Main balance before trading.

## Plan Types

| Feature          | Fixed Plans                             | Flex Plans                                 |
| ---------------- | --------------------------------------- | ------------------------------------------ |
| Lock-up          | 10, 20, 30, 90, 180, or 360 days        | None (withdraw anytime)                    |
| Interest         | Paid at maturity                        | Calculated hourly, credited daily          |
| Early withdrawal | Allowed — but **interest is forfeited** | Allowed — **accrued interest is retained** |
| Auto-reinvest    | N/A                                     | Available                                  |
| Auto-invest      | N/A                                     | Available                                  |
| API access       | B2B partners only                       | All authenticated users                    |

<Note>
  **Fixed plan API access:** Fixed lending endpoints (`/api/v4/main-account/smart/`) require B2B partner
  permissions. Complete the institutional services form to request access. Flex endpoints
  (`/api/v4/main-account/smart-flex/`) are available to all authenticated users.
</Note>

## Technical Overview

* **13 endpoints** total (5 fixed + 8 flex), all `POST`, all authenticated
* **Authentication:** HMAC-SHA512 ([guide](/api-reference/authentication))
* **Rate limits:** 1000 requests per 10 seconds per endpoint ([details](/api-reference/rate-limits))

For full endpoint documentation, see the [Crypto Lending API Reference](/api-reference/account-wallet/overview).

## Platform Context

The WhiteBIT platform brands lending products as **U EARN**. The platform also offers Staking and Auto-Invest for recurring purchases -- available via the [platform UI](https://whitebit.com), not the API.

## What's Next

<CardGroup cols={2}>
  <Card title="Quickstart" icon="rocket" href="/products/lending/quickstart">
    Create a first Flex investment in under 5 minutes.
  </Card>

  <Card title="API Reference" icon="square-terminal" href="/api-reference/account-wallet/overview">
    Full endpoint documentation for all 13 lending endpoints.
  </Card>
</CardGroup>