> ## Documentation Index > Fetch the complete documentation index at: https://docs.ulm.m1amdocs.com/llms.txt > Use this file to discover all available pages before exploring further. # Associate external billing account An existing, authenticated user associates their service billing account to their User ID (or "user profile" within your client application). \[product: dim]\[/product: dim] ## Initial Request Your client calls the [Process Start](c_processStart) API to initialize the Process: ``` **POST https://\{your.url\}/process/start/accountAssociation.AssociateAccount.v1.0** ``` ## Response: prompt for account identifier Digital Identity Management responds with a request for the a mobile number to identify the external accoun: ``` **RESPONSE - body** { "processId": "ec90ed2c-eca9-42de-9fbc-a81506c5d1e8", "processName": "accountAssociation.AssociateAccount.v2.0", "stepName": "IdentifierPrompt", "lastStep": false, "parameters": { "identifier": "string" } } ``` | `processId` | Unique identifier for the current instance of this Process. | | - | - | | `processName` | Full name of the Process, including the category and version number. | | `stepName` | Name of the specific step that the Process is currently on. | | `lastStep` | Boolean that indicates whether or not this was the last step in the Process. | | `parameters` | Object that specifies the info this Process requires to continue its task. | | `identifier` | Item that uniquely identifies the external account. Currently, this Process only accepts a mobile number. Support for email address and external account number are roadmapped for a near-future release. | ## Next Request: account identifier The user provides their mobile number, and the client passes that to Digital Identity Management in a [Process Step](c_processStep) API request: ``` **PUT https://\{your.url\}/process/step** { "processId": "ec90ed2c-eca9-42de-9fbc-a81506c5d1e8", "parameters": { "identifier": 5272096291, } ``` | `processId` | Unique identifier for the current instance of this Process. | | - | - | | `parameters` | Object that contains the data that was requested in the previous Process response. | | `accountKeys` | Object that contains the mobile number to identify the account in the BSS/OSS. | ## Response: issue OTP, return PKAT Digital Identity Management queries the external account system with the user-supplied identifier. If the external system returns an account, Digital Identity Management then generates an action token and delivers it to the mobile number for ownership verification. This Process returns a PKAT in its final response, and then ends: ``` **RESPONSE - body** { "processId": "ec90ed2c-eca9-42de-9fbc-a81506c5d1e8", "processName": "accountAssociation.AssociateAccount.v2.0", "lastStep": true, "output": { "pkat": "fe738030-e997-43e7-baad-fe7a386d91fd"    } } ``` **Note:** Any Process step that sends a Digital Identity Management action token also returns a corresponding [Proof Key for Action Tokens (PKATs)](c_actionTokens#section_irr_wss_cpb)(Proof Key for Action token) to the client application. In order to enable OTP verification on the UI, the client **must** retain the PKAT returned by the final Process step. The [Proof Key for Action Tokens (PKATs)](c_actionTokens#section_irr_wss_cpb), along with the user-supplied OTP, is required for the `GET /session/token?customToken={OTP}&pkat={pkat}` API to invoke the **Complete Account Association** Process. | `processId` | Unique identifier for the current instance of this Process. | | - | - | | `processName` | Full name of the Process, including the category and version number. | | `lastStep` | Boolean that indicates whether or not this was the last step in the Process. | | `output` | Object that contains data that the client can consume, retain, and use for additional operations. | | `pkat` | Unique Proof Key for Action Token that corresponds to an existing action token. See [Action Tokens](c_actionTokens) for more details.The client will need to supply this PKAT, along with the user-supplied OTP, in the next request in order to complete the account association. | ## Final Request The user retrieves the OTP from their SMS, and supplies it to the client application. The client then calls the [Session Token](c_sessionToken#) API, and supplies both the OTP and PKAT in the request URL: ``` **REQUEST - GET /session/token?customToken=123456&pkat=fe738030-e997-43e7-baad-fe7a386d91fd** ``` If both the OTP and PKAT are valid, this API invokes the **Complete Account Association** Process. ## Response: Process complete The Process performs creates the Digital Identity Management Account entity (and any Digital Identity Management Subscription and Digital Identity Management Feature entities, based on the integration and mapping between Digital Identity Management and the external system), and associates it to the user's profile (i.e., to their corresponding User entity). Additionally, Digital Identity Management will associate the Account/Subscriptions/Features hierarchy to a Digital Identity Management Group. The following conditions apply: * **If the user already has a Group (of which they are the Primary):** Digital Identity Management associates the A/S/F hierarchy to the Group. * **If the user does not yet have any Group:** Digital Identity Management automatically creates a Group, assigns this user as the Group Primary, and associates the A/S/F hierarchy to the Group. The Process then returns a `200 HTTPS` status, and ends: ``` **RESPONSE - body** { "processId": "c0fe9d0e-ad72-4663-becd-abee28ad33d3", "processName": "accountAssociation.AssociateAccount.v2.0", "lastStep": true } ``` | `processId` | Unique identifier for the current instance of this Process. | | - | - | | `processName` | Full name of the Process, including the category and version number. | | `lastStep` | Boolean that indicates whether or not this was the last step in the Process. | | **Parent topic:**[Associate Billing Account to User Process](../topics/c_associateBillingAccountV2) | | This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.