I have received second year in a row an underpayment letter from NJ. After further investigations it seems that for both years, 2020 and 2021, wages were incorrectly transferred from federal to state. It did not accounted for Cafeteria, FSA contributions, etc that are nondeductible for NJ.
Is this a known issue/bug? It is annoying that I have to pay penalties for 2-3 years underpayment.
