It is easy to forget where you’ve registered your domain, i.e. what company is the registrar for the domain.
One way to find out where the domain is registered is by checking the domain’s whois information. You can use the website https://who.is/ for this task.
On the website, use the search field near the top:
For many TLDs (.se, .nu, .com etc), you will see a box on top of the search results with the header Registrar Info, where you can see the name of the company that is the registrar of the domain. For domains registered via us, it most often states Oderland or Key-Systems GmbH (with is our subcontractor for .com domains among others).
For a .se domain, the result may look like this:
A .com domain may have information such as this:
If the registrar info isn’t visible, or if you see some other information in the box, please refer to the raw data presented further down on the page. The way this data is presented varies between different TLDs and registrars.