# Client
source: https://developer.mastercard.com/mastercard-processing-core/documentation/api-basics-section/client/index.md

Represents a physical person or a company that owns account contracts and card contracts. A client can also be constructed as a technical object without any connection to the real entity.

The client object stores the following information:

* Personal data, such as last name, marital status, and birthplace.
* Identification data.
* Contact data.
* Base address date.
* Company data.
* Embossed data.
* Custom data.

Tip: The operationId `createClient` does not require a phone number or embossing data.  
Some operations require the following fields:

* Phone number is used for transaction authentication.  
* Embossing data is used in requesting physical card production.  

This setup was designed to enable creation of a client object even when the customer's phone number is not known or present. You can update the client object according to your needs later.

#### Client Roles {#client-roles}

A client has two roles:

* **Owner**: A client who owns the account contract. This role typically includes the cardholder role.
* **Cardholder**: A client who owns the card contract but does not own the account contract.

#### Card Contract {#card-contract}

The following rules apply to card contracts:

* Have one owner and one cardholder (whom is typically the same client).
* Are linked to one account contract.

A client can have multiple account contracts, but every account contract must be linked to one client. Multiple card contracts can be linked to each account contract, but each card contract is connected to one account contract. A cardholder can have a card contract and be the owner of the account contract. A cardholder can also possess a card contract linked to a different account contract. This situation is illustrated in the diagram below.
![](https://static.developer.mastercard.com/content/mastercard-processing-core/uploads/processing_8.png)

The methods used for the client object are illustrated in the diagram below:
![](https://static.developer.mastercard.com/content/mastercard-processing-core/uploads/processing_9.png)