Since it was received in 2023, it would be shown - IF it was taxable - on your 2023 return. Individuals are "cash basis" taxpayers. A state tax refund is taxable only if you received a tax benefit from deducting it. Did you itemize your deductions in 2021? Or did you claim the standard deduction? If you itemized, it would generally be taxable. If you claimed the standard deduction, it would not be taxable.