My question involves employment and labor law for the state of: Massachusetts
This is a little complicated so I will try to be clear. Two months ago I gave my notice to my employer, but because it was short notice, I agreed I would work part-time for a period in order to give them some flexibility while they found my replacement. I worked 3 days a week for the first two weeks, and one day a week for the last 6 weeks. Today is my last day and I just realized (have direct deposit and never looked at an online bank statement because I have been very busy with school, paying all my bills electronically) that they have been paying me a rather large sum for this second 6 week period, and I suspect that there was a payroll mistake. I know in most circumstances, I would be legally obligated to pay any overpayment back to my former employer, but in this case we never agreed to a contract regarding wages in this transition period. When I was first hired as salaried employee, I was working 3 days a week, later it became a full time position. I signed a formal contract when I was first hired (but not when I went to fulltime with different benefits), and I simply assumed they would pay me based on that original rate and pro rate to 1/3 when I went to one day a week. I assume I need to pay this back, and want to do the right thing, but I'm a broke student again and that money could come in handy for rent down the line if I dont have to return it.

