Chop saws are notorious for not making square cuts . Check to see if it's off square vertically or horizontally . If it's off horizontally, you should be able to adjust it's base to compensate . Vertical cuts usually have a tendency to be off due to the blade flexing as it goes through the steel . If you take your time you can make them pretty good , but overall these saws are only meant for rough cuts . That's why a good large bandsaw costs $1,000 .
Sarge