I had to repay UCCB in 2017. When entering this in TurboTax, my federal refund increases, but not the provincial (Quebec). Should this not also lower provincial tax?

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UCCB repayments lower your taxable income. Depending on your income taxes payable, non-refundable tax credits, and additional contributions or premiums payable to Quebec, the repayment amount may not lower the balance owing/refund. For example, if you had to pay the QC prescription drug plan premium. 

To verify if the UCCB repayment amount transferred correctly on the Quebec return, go to: 

Review > Bottom Line Summaries > Detailed Tax Summary (bottom left link) > Quebec Detailed Tax Summary (blue button on the bottom) > Line 297 Miscellaneous deductions.