Does the regular CTC change as the ACTC changes? 

Ive been tinkering around with my daughters return, shes only got 2 kids and she gets 2342 in CTC and 1658 in ACTC (total of 4000) 

When I add 50k in dividends, her CTC goes up to 4000 and her ACTC goes down to zero.

So if your CTC is maxed out, you wont get an ACTC.