After entering all information for sale of principal residence except for ACB (house was bought 50 years ago, principal residence for all the years owned), Turbotax will not continue to the next screen unless ACB is entered. I phoned CRA and they told me ACB is not necessary if only the first box is selected in Schedule 3 (which Turbotax did). I tried setting up a new account using Forms input, and same problem exists when going through the Review step.  I tried entering zero as ACB but Turbotax does not accept this either.