# Internal transfers

Move trading balances between Polyester accounts without touching a chain.

`client.internal_transfers` moves funds between Polyester accounts without touching a chain: from your source scope to another root account, a subaccount, or a smart-account address.

Transfers are idempotent on `idempotency_key`: repeat requests with the same key return the existing transfer instead of creating a second one. Quantity must be an `AssetAmount` in the ledger domain.

## Methods

| Method   | Summary                                             |
| -------- | --------------------------------------------------- |
| `create` | Create (or return) an idempotent internal transfer. |

### Create

Provide exactly one destination: `destination_account_id`, `destination_subaccount_id`, or `destination_smart_account_address`.

```rust
use polyester::models::CreateInternalTransferParams;
use polyester::types::{AssetAmount, QuantityDomain};

let quantity = AssetAmount::from_decimal_str(
    "125.50",
    2, // input/catalog precision
    QuantityDomain::LedgerE18,
    Some(2), // asset_id
)?;
let result = client
    .internal_transfers
    .create(CreateInternalTransferParams {
        asset_id: 2,
        quantity,
        idempotency_key: "xfer-stable-1".into(),
        subaccount_id: None,
        destination_account_id: None,
        destination_subaccount_id: Some("123".into()),
        destination_smart_account_address: None,
        quantity_scale: Some(2),
    })
    .await?;
println!("{} {}", result.transfer_id, result.request_id);
```

The second constructor argument and `quantity_scale` describe the input precision. If `AssetAmount` already carries a scale, `quantity_scale` must match it; when the amount has no scale, the option supplies one. The final `Some(2)` constructor argument is the asset ID.

The request field is always canonical 18-decimal `amount_e18`. The SDK rescales exactly: it rejects overflow, zero values, and downscaling that would discard non-zero digits. It never rounds.

## Related

- [Deposits & withdrawals guide](https://testnet.polyester.com/docs/sdk/rust/guides/deposits-and-withdrawals)
- [Balances](https://testnet.polyester.com/docs/sdk/rust/reference/balances)
- [Withdrawals](https://testnet.polyester.com/docs/sdk/rust/reference/withdrawals)
- [Requests & idempotency](https://testnet.polyester.com/docs/sdk/rust/concepts/requests-and-idempotency)