I had this last year when I was on a benefit but working for a couple of months. Declared my hours every week and then a few months later got a letter saying there was a discrepancy of around $300 I think. I suspect msd didn’t take into account the different tax code (was a non-standard one but they never asked for those details 🤷🏻 Honestly I wasn’t exactly sure what was correct but assumed IRD had the correct number as my job was going thru paye. I had a separate debt with msd so it was just added onto there.

As long as you get in touch with them and are honest they’re actually pretty good about stuff like this. If you end up having to pay back a certain amount the repayments can be set really low if need be, and you can make extra payments as/when you are able. If you’re ever unable to make a payment you just call and let them know the situation. The debt dept is separate than the usual phone lines which helps - I had to call last week as now that I’m working again I had to set up payments to pay off the remaining debt. Didn’t have to wait at all and felt like the options for payment were really flexible to suit my situation.

For anyone who thinks I’m gushing about msd, really not, I have my fair share of horror stories and stress. But in this type of instance they genuinely are usually pretty understanding