It is a sin not to pay tithe. Tithe is a commandment from God so every christian is expected to pay tithe.
the breathe we breathe, we are not paying for it, the only thing that God demanded for us is to pay our tithe, God does not need our money, the tithe is to be used to keep the house of God in order.

So my brother, if you are not paying tithe, know that you are disobeying God.