If you received the refund in the same year that you paid the dues, you do not have to report it. For example, if you received a refund in 2018 of dues that you paid earlier in 2018, there is nothing to report.
If you received a refund of union dues that you paid in an earlier year, you might have to report the refund as income on your tax return for the year that you received the refund. You would only have to report it if you claimed an itemized deduction for union dues in the year that you paid them. In that case, the refund is called an "itemized deduction recovery." The amount you have to report as income is not necessarily the full amount of the refund. It's only the amount for which you actually received a tax benefit from the deduction in the earlier year. IRS Publication 525 explains how to calculate the taxable amount, in the section on "Recoveries," and it has a worksheet to do the calculation. TurboTax will not do the calculation for you. If you did not itemize deductions in the year that you paid the dues that were refunded, or you itemized but did not claim a deduction for the dues, you do not have to report the refund. Note that for 2017 and earlier years, the deduction for union dues was a miscellaneous deduction subject to the 2% of AGI limitation. That means that even if you listed the union dues on Schedule A, you did not actually get any tax benefit from the deduction unless your total miscellaneous itemized deductions were more than 2% of your AGI.
If you received the refund in the same year that you paid the dues, you do not have to report it. For example, if you received a refund in 2018 of dues that you paid earlier in 2018, there is nothing to report.
If you received a refund of union dues that you paid in an earlier year, you might have to report the refund as income on your tax return for the year that you received the refund. You would only have to report it if you claimed an itemized deduction for union dues in the year that you paid them. In that case, the refund is called an "itemized deduction recovery." The amount you have to report as income is not necessarily the full amount of the refund. It's only the amount for which you actually received a tax benefit from the deduction in the earlier year. IRS Publication 525 explains how to calculate the taxable amount, in the section on "Recoveries," and it has a worksheet to do the calculation. TurboTax will not do the calculation for you. If you did not itemize deductions in the year that you paid the dues that were refunded, or you itemized but did not claim a deduction for the dues, you do not have to report the refund. Note that for 2017 and earlier years, the deduction for union dues was a miscellaneous deduction subject to the 2% of AGI limitation. That means that even if you listed the union dues on Schedule A, you did not actually get any tax benefit from the deduction unless your total miscellaneous itemized deductions were more than 2% of your AGI.