# Coupon Token

{% hint style="info" %}
**Source:** `src/fira_bonding/core/YieldContracts/CouponToken.sol`
{% endhint %}

## Token details

| Property | Value              |
| -------- | ------------------ |
| Standard | ERC-20 (FiraERC20) |
| Symbol   | CT                 |
| Decimals | 6                  |
| Permit   | No                 |

## Key view functions

| Function              | Returns                                          |
| --------------------- | ------------------------------------------------ |
| `bcIndexStored()`     | Last cached BC index                             |
| `bcIndexCurrent()`    | Current BC index (may trigger update)            |
| `isExpired()`         | Whether BT/CT have expired                       |
| `FW()`                | Associated FW token address                      |
| `BT()`                | Associated BT token address                      |
| `getPostExpiryData()` | Snapshot data from first post-expiry interaction |

## Interest tracking

Interest is distributed on every transfer via `_beforeTokenTransfer`. Users claim via `redeemDueInterestAndRewards`. The `interestFeeRate` is deducted at claim time.

## Related pages

* [CouponToken (Protocol Contract)](https://docs.fira.money/developers/protocol-contracts/yield-contracts/coupon-token)
* [Coupon Token (Feature)](https://docs.fira.money/developers/features/coupon-token-ct)


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