When an unbeliever comes to Christ, Jesus become his mediator of the New Covenant. A believer cannot enter into this New Covenant without his sins being atoned for. Jesus atoned for man's sins past, present and future. I seems Jesus make a person free or exempt from sin from the day of their new birth. At birth we've recieved a new heart and a new spirit. Sin cannot occupy any place where the Spriit of GOD is. Sin corrupts, and our new heart cannot be corrupted by sin. This is why Jesus had to remove and take away sin. This is why He removed the law, because only by the law is the knowledge of sin. It's not that we don't to wrong things, the fact is GOD is not imputing sin unto believer.
Eze 36:26 A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
Rom 4:8 Blessed is the man to whom the Lord will not impute sin.
Greek definition of 'Impute:" This is what Jesus is not doing where it pertains to sin.
G3049
log-id'-zom-ahee
Middle voice from G3056; to take an inventory, that is, estimate (literally or figuratively): - conclude, (ac-) count (of), + despise, esteem, impute, lay, number, reason, reckon, suppose, think (on).