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

# Collateral and yield

> Your deposit is held as yield-vault shares, so it grows.

## How collateral is held

When a top-up is credited, its AUSD goes into an **ERC-4626 yield vault**, and the vault shares are recorded as your collateral. Their value is read with the vault's own `convertToAssets`, so no outside price oracle is involved.

| | Testnet | Mainnet (planned) |
| - | - | - |
| Vault | MockEarnAUSD | earnAUSD |
| Yield source | Whatever the operator pays in, to show the mechanism | Trading strategies (basis trade, delta-neutral) |
| Withdrawals | Instant | Can queue up to 72 hours |

## The yield fee

Borrowing is interest-free. Instead, the protocol keeps **20%** (`yieldFeeBps = 2000`) of the yield your collateral earns. It is charged when collateral leaves or changes, and it is what lenders earn for funding the line.

Your collateral value, and so your limit, is always shown **net** of the fee already accrued.

## Taking collateral out

`withdrawCollateral` redeems the vault shares you name and sends you the AUSD, as long as your debt stays within your new, lower limit. With no debt, you can withdraw everything.

## If the vault loses value

Your collateral value falls, and your limit falls with it. If you are now over your limit, new draws are blocked, but **you are not defaulted** for it: default only ever follows a missed due date.


This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.