Changing your location late for income tax purposes

Hi guys! A friend of mine not on reddit had a question.

They got a job at a company out of state and were able to start working from home from state A. After a few weeks of this they were able to figure out how to move to state B, which is where their job is actually located.

Unfortunately, they did not change their address on the company records until months after out of negligence. This means that they were getting taxed as though they were in state A although they had moved to state B for quite some time. Are there any consequences of this? What can be done about this?