The Partner ID is a four-digit number. It is used for identification and as a username for the main user.

You will receive the Partner ID after signing the contract and creating your account. The Partner ID will be sent to you by e-mail with your access data. After you have logged in, you will also always see Partner ID in the upper right part of your Control Panel:

If you are not the main user of this account, you will find the partner ID with the invoices. The partner ID is always the first four digits of an invoice number. You can find the invoices in your control panel in the passive menu part under "Invoice and payment":