Dress codes for many workplaces today are a far cry from the styles of the 1950s where men wore dark suits and women wore skirts and dresses. Jeans are common in many offices, a cultural change ushered in alongside the rise of the tech industry in the 1990s. The rule of thumb when going for a job interview at a new place is to dress one step better than the prevailing office climate. If you already work in an office and are seeking a promotion, deciding what to wear to an interview can sometimes be a problem.
If you dress too informally, you might create the impression that you don't care about the job you are seeking. Formal attire may make the interviewer seem under dressed. One benefit of a job interview within an organization you already work in is that you already know what the dress parameters are.
Err on the Side of Formal
It doesn't hurt to err of the side of formal attire. If open collars are common in the office, but ties are not, wear a tie or a jacket. According to a tip sheet compiled by Hull Strategies, "It’s better to take a little kidding from your friends about dressing up for the interview than for the interviewers to think that you didn’t care enough to do so."
Consider the Position
In some workplaces, attire may be informal for some jobs and formal for others. It might, for example, be acceptable for tech support to wear t-shirts while the accounting department wears more traditional business attire. If the job you are interviewing for usually comes with a change in dress code, then dress the part.
If you have a mentor in your organization, and you have been asked to interview for a position, it doesn't hurt to ask about proper attire. This might be simple. If the interview is unscheduled, mention to a supervisor that you would like a few days' notice to go shopping for a new suit. He may tell you that a suit isn't necessary. If you are talking with an internal mentor about the job and its responsibilities, that might be a good time to ask if the position comes with a change in wardrobe.