A tax refund is generally not considered taxable income, so you do not need to declare it on your 2026 return unless you itemized deductions on your 2024 return and that refund represents a recovery of state taxes that previously lowered your federal tax bill. Note- many taxpayers were limited to $10,000 in state and local taxes in 2024, yet had much higher income tax expenses. If that applies to you, you may not have received a benefit of the tax this refund is attributable to.
If you did itemize deductions on your 2024 return and received a benefit of the state tax deduction, you must report the state refund as taxable income on your 2026 return because that is the year you will actually receive the funds.
Do you mean a federal refund? You do not enter anything about a federal refund on your federal tax return.