Got an overpayment notice, what now? - first time posting

After 6 weeks of benefits I got a notice saying I must repay some of it. There are 14 people counting on me, so I am trying to be careful. I did not notice any errors at the time. Has anyone disputed one of these?

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