Do I have to repay an overpayment of unemployment benefits?
If you were overpaid—that is, if you were paid benefits to which you were not entitled—then yes, you are responsible for repayment. It’s as simple as this: you have no right to that money and therefore must return it. It’s no different from expecting an insurer to return or credit back part of your premium if you overpaid, or expecting a store or contractor to return money that you overpaid for goods or a service.
If accepting the overpayment was innocent on your part (e.g. you did nothing to cause it to happen, and also did not previously realize it was an overpayment) then you should not be liable for anything other than the return of the money. It would also be appropriate for a repayment schedule to be worked out in that circumstance, rather than expecting you to repay it all at once.
The situation would be different though if you caused it to be an overpayment (e.g. deliberately filled out our claim using inaccurate information that caused you to be paid more than you were entitled to) or even knew all along that it was an overpayment but accepted it nonetheless. In either of those circumstances, you might be accused of fraud and potentially be liable for either additional penalties or possibly even criminally.
In the former case of innocent overpayment you could directly approach the unemployment office and see if you can work out a repayment schedule. If you're uncomfortable doing this, or the office is being uncooperative, an attorney can help you. Note that delaying after you’re now aware of overpayment could result in your actions no longer being viewed as innocent.
In the latter case, you should definitely speak with an attorney about the best way to proceed to protect your interests. An attorney experienced in unemployment matters can advise you as to any potential liability and also negotiate with the unemployment office on your behalf.
You also might speak with your tax preparer. If you paid taxes on your unemployment compensation, you may be due some credit or adjustment now that you are repaying an overpayment.