If you type in an Organisation name that already exist in the system, you will be notified, and cannot create the Organisation.

As default, the duplicate validation is on Organisation name + Divison name (if Division is activated). You can change these settings yoursekf, by going to Configuration → Custom Fields → Organisations and click on the duplicate icon at the top of the page.

Be aware, that the name has to be the exact same, for the duplicate validation to notify you. If you have the need to create two Organisations with the same name, you can use Divison to for example seperate the two departments. In the example below, we called this webCRM department UK in divisin name, to set the two departments from eachother.

To change the settings of the duplicate validation, go to Configuration → Custom fields → Organisations and then click on the duplicate icon, on the top of the page.