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# Client Profiles

* [Previous](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/)
* [Next](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/account-customizations/)

### What is a client profile?

A client profile allows you to customize how the AFC tax engine interprets a request and returns tax results. [Customizations](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/account-customizations/) include:

* Bundle
* Exclusion
* Tax Override
* AFC Tax Engine configuration

### Why use a client profile?

Reasons to use a client profile include:

* Profiles are cached - this speeds up response times
* Using a client profile eliminates including the same customization, such as a [tax override](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/sample-transactions/tax-override/), in each [CalcTaxes request](https://developer.avalara.com/communications/dev-guide_rest_v2/reference/calc-taxes-request/)

1. [Request](#request) a client profile containing [customization file(s) and configurations](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/account-customizations/) be added to your client
2. Specify the `client_profile_id` in the [header](https://developer.avalara.com/communications/dev-guide_rest_v2/getting-started/authentication/) to apply the client profile to all requests run using that header

* Multiple profiles can be applied to your client ID. Examples uses for multiple profiles include:
  * Separate configurations for different different types of transactions
  * Separate configurations for child companies
  * Testing new configurations

### How to apply a client profile to a session

When [authenticating](https://developer.avalara.com/communications/dev-guide_rest_v2/getting-started/authentication/) to Communications REST v2, pass the client profile ID in the header using `client_profile_id`.

#### Postman example

Add these [headers](https://developer.avalara.com/communications/dev-guide_rest_v2/getting-started/authentication/) to your request:

* `Authorization` using basic HTTP authenticNoteation
* `client_id`
* `Content-Type: application/json`
* `client_profile_id`

![](https://developer.avalara.com/public/images/comms/dev-guide_rest_v2/postman_headers_profile.png)

### How to run transactions without a profile

REST v2 uses the system default profile when a profile is not specified.

To send a transaction without a client profile, modify the [header](https://developer.avalara.com/communications/dev-guide_rest_v2/getting-started/authentication/) using one of these options:

* Do not include `client_profile_id`
* Set `client_profile_id` to "0"

#### Note

The system default profile is "0".

* [Previous](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/)
* [Next](https://developer.avalara.com/communications/dev-guide_rest_v2/customizing-transactions/account-customizations/)

> **Note**
>
> Part of the **Communications REST v2 Developer Guide** integration guide. [Open the full "Client Profiles" milestone on Avalara](https://developer.avalara.com/products/communications/integration-guides/dev-guide_rest_v2/customizing-transactions/) to see every page in this section.