When calculating income for tithing, should one include money received as child support?
Tithing is 1/10th of your increase or income. However, these funds are meant to be used in the support of your children and not for yourself. You are given stewardship over the proper use of these funds, but they are not your funds, nor is it an increase for you.
If you are using child support funds for any of your own personal needs, then the amount of your own use should be tithed. Otherwise, you are simply the administrator and manager of these funds on behalf of someone else (your kids).
You are always free to ask your Bishop for advice in this area as well. Remember that in tithing settlement, your Bishop will only ask if you’ve paid a full tithe. It’s up to you to determine what that means. The Bishop isn’t going to ask you for a copy of your tax returns to verify all sources of income. It’s between you and the Lord, with the Bishop acting on the Lord’s behalf.
Hope this helps!