# token.lock()

[[Source]](https://github.com/ripple/simpleXRPL/blob/95b977b15f8950c5bc076b25165217869c0b06d3/src/verticals/token.ts#L202)

Lock an MPT issuance, or a specific holder's balance when `holder` is given.

## Signature


```ts
token.lock(
  params: TokenLockParams,
  options?: TokenWriteOptions,
): Promise<SubmissionResult>
```

## Parameters

| Parameter | Type | Required | Description |
|  --- | --- | --- | --- |
| `mptIssuanceId` | `string` | Yes | The MPT issuance id. |
| `holder` | `string` | No | A specific holder to lock. Omit to lock the whole issuance. |


## Options

`options` is an optional second argument that sets the source account and overrides the fee.

| Option | Type | Required | Description |
|  --- | --- | --- | --- |
| `from` | `AccountSelector` | No | The account to act as — an r-address string, or an object `{ address }` or `{ signer, account? }`. Defaults to the primary signer's primary account. (For IOU operations, this is the issuer.) |
| `fee` | `FeeIntent` | No | Fee override — a priority tier and/or a `maxFeeDrops` cap. |
| `idempotencyKey` | `string` | No | A prior submission's `idempotencyKey`, to retry to the same intent instead of creating a duplicate. Auto-generated when omitted. |


## Returns

Resolves to a `SubmissionResult<{ mptIssuanceId: string; locked: boolean }>`.

Every simpleXRPL write resolves to a `SubmissionResult<T>` — a union tagged by `source`, with the backend's raw response preserved verbatim. Its common fields are:

| Field | Type | Description |
|  --- | --- | --- |
| `intent` | `T` | The operation-specific output — see the operation's own return fields. |
| `source` | `'xrpld' | 'custody' | 'palisade'` | Which backend produced the result; discriminates `response`. |
| `response` | `TxResponse` | custody record | Palisade record | The backend's raw response, preserved verbatim. |
| `txHash` | `string` *(optional)* | The XRPL transaction hash, once the transaction is on-ledger. |
| `intentId` | `string` *(optional)* | The custodian intent id, when the path produced one. Hold onto this to resume via `client.intent`. |
| `idempotencyKey` | `string` *(optional)* | The UUIDv7 this submission carried. Pass it back as a later call's `idempotencyKey` to retry to the same intent rather than creating a duplicate. |


### Return fields

For `Token.lock`, the `intent` carries:

| Field | Type | Description |
|  --- | --- | --- |
| `mptIssuanceId` | `string` | The MPT issuance id that was locked. |
| `locked` | `boolean` | The resulting lock state (`true`). |


## Underlying XRPL transactor

Builds and submits a single [MPTokenIssuanceSet](https://xrpl.org/docs/references/protocol/transactions/types/mptokenissuanceset) transaction with the lock flag set.

## Example


```ts
await client.token.lock({
  mptIssuanceId: '005C...',
})
```