Some people have asked me if it’s necessary to wear a suit to an interview. My personal opinion is that every adult should own at least 1 full suit and said suit should be worn for interviews. It’s true that various sectors are more laid-back than others and might have a more relaxed office dress-code but you can take advantage of that once you’ve been offered the job.
You never know who you will encounter during your interview and what their personal preference will be. People make snap judgments when they first meet you, especially when you’re going in for an interview. What if you interview with the one guy in the office that although there is a business casual dress-code still believes in business professional attire everyday? That person will probably think to himself, “I would have worn a suit to an interview,” and now you’ve started off on the wrong foot.
Aside from that, there are various degrees of business casual all subject to your employer’s personal opinion. At one job I was told that business casual meant having a blazer everyday. I kept a black blazer on the back of my chair. At another job I was told that I just had to look “neat and professional,” (slacks, skirts, collared shirts, etc.). The point here is that what was considered business casual at one place wouldn’t have been at another. Do you want to take that chance at your interview?