I hope this hasn't caught you out @Michael, but in Sunday's race I missed that I had to use 2 tyre compounds at the race (I hadn't realised this previously but just so happened to use 2!).
I finally finished in the points, but got a message yesterday that I had been disqualified.
Unfortunately, the penalty is pretty hard:
I lost my Championship point
I also lost ALL prize money for both cars, even though the first one retired with a mechanical failure.
So... after my sponsor rant the other day, I am now another £650,000 down on prize money for entering the race.
Costly mistake
If you go to Championship > Rule Book - you will find a line in there telling you about two types of compound.