I heard about security clearances and drug tests that larger companies do for their new hires. Why is it necessary and will they do this before the interview or after an offer is made? I've never been drug tested before so I'm curious if companies are usually transparent about it during the interview process.
I work in the financial industry. My company drug tests every employee in every department (they pay for the test, but you can't start till you've passed it) and we also have a background check done, looking specifically for financial or fraud issues. However at my previous job, there was no testing and much larger volumes of money passed through the system there. I don't think there's a hard rule, but I believe most companies do test for drugs. I would say be prepared to be tested. It's not really something you can ask during the interview without throwing some red flags.