# Required IDs for attribution

## Required & Optional IDs

| Data source / tables | Required IDs                                                  | Optional IDs                                               |
| -------------------- | ------------------------------------------------------------- | ---------------------------------------------------------- |
| Sessions             | <p><code>anonymousID</code></p><p><code>userID</code></p>     | `customerID`                                               |
| Users                | `userID`                                                      | <p><code>anonymousID</code><br><code>customerID</code></p> |
| Revenue              | <p><code>customerID</code></p><p><code>userID</code></p>      | `anonymousID`                                              |
| CRM                  | <p><code>contactID</code> </p><p><code>anonymousID</code></p> | <p><code>userID</code><br><code>customerID</code></p>      |

### Roadway solutions

We provide simple solutions for you to add missing and hard-to-route IDs to make it easy for you.

#### [Add Anonymous IDs to CRM contacts](https://docs.roadwayai.com/required-ids-for-attribution/implementing-the-roadway-tag)