No matter how many times I correct the 'fix' you demand it still keeps coming up as an 'error' and won't let me Netfile

[dennisryoung]

I keep putting the number of months in box 21 but you keep telling me it is an error.

[TurboTaxMonica2]

Did you enter multiple T4A's? And did you receive the amount due to disability or retirement?

[TonyC11]

You should only be entering a number in box 21 if you received any CPP Disability payments in 2018.
This box should NOT be filled simply because you are entitled to Disability Tax Credit. That is a different item.
Also, boxes 21 and 23 cannot total more than 12 on your T4A(P).