If you consistently demur on the extra little tasks your boss asks you to do then don't be surprised if you don't move up in the company.
As a manager, the one refrain you don't want to hear is, "It's not my job." If something is asked of you and it is either outside of your skill set or you really don't have the time to do a bang-up job of it, then it's okay to tactfully explain that to your boss. But if that is your motto every time you're asked to do something, then don't be surprised if you don't move up in the company.
I have encountered two extremes of the work ethic -- those who for some reason won't take on any tasks that aren't directly related to their official jobs, and the eager-to-please who take on anything that is thrown out there with no regard for their own time restraints. I'll address the latter in another blog post, but for now we'll talk about the "not my job" guy.
The compartmentalized employee
Before I hear from everyone telling me how, if you don't put your foot down, you'll end up with more work than one person could ever finish, let me explain. It is true that some managers fall easily into the trap of accepting new duties on behalf of the team in order to look better in the eyes of his or her superiors and then pass everything on to the team. And sometimes IT pros find that when they switch job roles, whether due to a promotion or a lateral move, their old duties seem to follow them.
Years ago, a guy came to my team who had previously helped the marketing department set up a database. Although the manager in the marketing department had promised to hire someone to take over the database responsibilities and upkeep, she didn't do it -- at least not for months. What she thought of as a few "can you take a looks" ended up taking a significant portion of this employee's time from his new duties. However, instead of outright refusing her, he came to me, explained the situation and said that if I, as his new boss, wanted him to keep working on the database, he would but it would be a hardship. I agreed with him and had a talk with the old manager who ended up hiring someone.
What I'm talking about in terms of "it's not my job" is the person who doesn't understand the team concept. Also a few years ago, the receptionist at a company where I worked went through a health crisis. She tried to come into work everyday but there were a couple of instances when she had to unexpectedly leave early. This meant that it fell to whomever was left to let people in when the door buzzer sounded. One person said that it wasn't her job to answer the door.
That's true, it wasn't. It was no one else's job either. But it was an extraordinary circumstance that we all, as employees, should have helped mitigate. Her unwillingness to step up to the plate like everyone else stayed with me. In business, particularly in small start-ups where everyone is doing everything for a while, it becomes fairly obvious who you can count on.
At some point, the refusal to do extra tasks can become an ego issue: "I'm above that sort of thing." But I will guarantee you that no boss will look back at your work history and be impressed that you stayed true to your narrow view of your own duties. You will come across as inflexible and not open to new things. If a promotion is what you're seeking, those two traits are not ones you want to perpetuate.