Can I claim repayment of Child tax benefits (had been overpaid in previous years and paid that back in this year)

If it is a repayment of the Universal Child Care Benefit, you will have the amount showing in box 12.  If it is a repayment of the non-taxable Canada Child Tax Benefit (CCTB) then you are not able to claim a deduction.

Sorry - I don't know what you mean "showing in Box 12"  box 12 where?   It is both CCTB and UCCB I am repaying so I understand I won't be able to claim both... but where should I be inputting this deduction?   
I'm also wondering if there is somewhere in Turbo Tax where I could view what I have done so far in a form format.  Maybe that's what you're referring to with saying to look at box 12?

Thanks!