It depends on your fed and local organization. I just took the written test for IPF for the 'entry level' but still have to do the practical. There are different levels i.e. provincial, national, international that can only be achieved (in the IPF) by reffing at a level for a period of time (sometimes years) and a certain percentage of the lifts you ref must be squats.
However, the written test was created locally by our Provincial referee chairperson and other provinces have their own tests so standards may vary.
Most of our refs are current or former lifters and typically. If you're interested contact your local fed. I found having to learn the minutiae of IPF rules very helpful even if you aren't going to ref.