But my dad and mom often made extra money, beyond salary or wages -- my dad from his sign painting and photography, my mom from typing dissertations and other projects.
My dad explained once that in defining the tithing on a one-shot, part-time sign painting job, he really should deduct, as any other business does, the cost of materials. "But that feels to me like nickel-and-diming the Lord," he said, so he didn't bother making deductions -- he tithed on the whole amount he was paid. "Still, wouldn't be wrong if somebody else chose to deduct those costs," he explained.
He told me that when he owned an actual sign-painting company, he based his tithing on the income after deducting the costs of employees, equipment, and so on. "The company didn't pay tithing on its gross receipts, I paid tithing on the portion that was my increase."
That's what he believed was right, after prayer and consultation -- with my mother first, and then, together, with the bishop.
As I got older, I learned what tithing money was used for, and the many spiritual and temporal reasons why it's essential to pay that 10 percent.