When Paying Tithe On Your Net

We should pay tithes on our refund checks because it's money the government is giving us because they overtaxed us, so really, that money is part of our gross pay, so if we're paying tithes on our net because the government taxes the gross, with the refund, it allows us to pay the money that was part of the gross that we didn't pay tithes on because we never saw it