My T3 form has error that box 52 (total capital gains before end of June) & box 53 (gains after June) don't equal total capital gain box 21. 1208.51+1095.17<>2303.68?
For the error on the T3 slip not balancing box 52+53 to equal box 21A, trying to enter the sum of 52+53 into box 53 (deleting 52) should fix the problem.
