Got an overpayment notice, what now? - what worked for you?

The agency says I reported earnings incorrectly, but I think I followed the instructions. There are 13 people counting on me, so I am trying to be careful. I did not notice any errors at the time. Are payment plans possible?

Thanks for writing this out. I went through something close to it 13 months ago, and it settled down once I kept a simple log of every call and form.