You will report T4 income from a T4 slip only.
For contract income that you do not receive a T4 or T4A slip for you will have to claim that as self-employment income on a business statement. Do not add that income to a T4 as additional income.
If you are asking how to claim on your return then yes, add his T4 Box 14 income together with his self-employment income (if there were no expenses claimed) to arrive at his net income as long as there were no other deductions like contributions to an RRSP or union dues paid.
It is always better to prepare both tax returns together at the same time so that you don't have to copy over this information from one return to the other.
