Project customer relationships help you manage projects that involve multiple clients by specifying the various relationships your customers can have with a project. A customer has exactly one relationship with a given project; one or more customers can have the same relationship with a project.

For example, most projects have a single customer who is the main client on the project; you can define a relationship with a name such as Primary to indicate the major client on a project.

Contact types specify how the contacts of a particular customer are involved with a project. You can use project contacts to direct certain pieces of correspondence, such as invoices, to the appropriate customer contact.

For example, if your client identifies a specific employee as the technical resource for questions about that client's project, you can classify that employee using a contact type. First, you create a contact type with a name such as Technical. Later, when you define a project or modify your definition of that project, you assign the Technical contact type to the appropriate customer contact.

 Pre requisites
First create a contact for the customer

 Next, add the customer bill to contact at the project level.

Oracle Projects predefines two contact types:

1. Billing
2. Shipping

Oracle Projects addresses invoices to the billing contact you specify when you define a project. All contract projects require a billing contact.