I received a 1099G 2016 state form for the first time and it says it may be taxable on my federal return if I deducted the amount of Louisiana tax as an itemized deduction on federal return. How do I enter this and will it have a specific impact?

It may or may not be taxable.  It is taxable if you itemized deductions last year.  If you took the standard deduction it is not taxable.  If you Itemized and took the state income tax deduction instead of the sales tax deduction on sch A line 5 you got a deduction for it.  So now the refund can be taxable.

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