Company Started Paying Me Again (i Am No Longer Under Contract.) I Reached Out Twice. Now What?

Location: Massachusetts. Company in question is in NYC.

I was a contractor for a massive company but my work ended there 18 months ago or so when project was over. The unit I worked for spun off recently. Around the same week that happened the original big, bureaucratic parent company randomly paid me my former installment based on that lapsed contract. They did this via a direct deposit.

I immediately notified my only real contact, who now works for the spun-off company. He treated it as probably a one off payment, and maybe I was owed it, and basically said enjoy it. This was on text.

Then I got paid a second time. Each time I get an automated email saying the payment is coming. This second time I immediately replied to that email explaining what happened and that they probably want to stop it.

It went to some payroll IT department. They created a “ticket” and a day later they closed the ticket and replied to me there is nothing they can do and I need to reach out to my contact within their company. (I don’t have one.) This was all on email.

Beyond going back to my original guy at the new company and pressing him for a better contact .. what do I do here? I am fully aware I will pay taxes on this money if this goes on.

1. When does my obligation end to proactively fix their error?

2. When would I ever be in the clear to treat this as a windfall?

3. What legal issues or problems am I not seeing? I am not divorced paying alimony or have debts that involve income based payments.

4. I’ve kept the money in the checking account they made the direct deposit to. It makes no interest, so can I move it and just not spend it or should I never touch it?

Context: this adds up to about 70k pretax a year. Remember I was a contractor so they pay no taxes or benefits on my behalf. And,not that it matters, but I don’t need this money and certainly don’t want headaches as a result of being cute about it. I don’t have any idea what I would even spend it on so my main thought is to give all post-tax to charity at the point it does look like I could keep it.

Just don’t want to be stupid.