The sin debt of mankind has been paid; Christ Jesus accomplished this on the cross of Calvary when sin was judged by God.1 It was judicial judgment of sin, as we would see in a courtroom.
Although judicially God has judged sin, in order to receive God's forgiveness, we must abide by His verdict, which is: "For God so loved the world that He gave His one and only Son (Jesus), that whoever believes in Him shall not perish but have eternal life. For God did not send His Son into the world to condemn the world, but to save the world through Him. Whoever believes in Him is not condemned, but whoever does not believe stands condemned already because he has not believed in the name of God's one and only Son." 2
When we truly turn to God in repentance through faith in Christ Jesus as Lord and Savior, God, at that time, applies judicial forgiveness of sin to our lives (once and for all time); God no longer holds our sin against us as to our salvation.3 He, also, adopts us into His family.4
God's adopted children, from time to time, give into temptation, fall into sin, and need their Heavenly Father's forgiveness5; we refer to this forgiveness as parental forgiveness (God being our Heavenly Father.)
Parental forgiveness is not the same as judicial forgiveness. Judicial forgiveness has to do with one's salvation, whereas, parental forgiveness has to do with one's standing in the family of God; it's the same as we would ask of our earthly parents; when we have done something wrong, are sorry for what we have done, and seek their forgiveness.
1 (John 1:29; Hebrews 10:12)
2 (John 3:16-18 NIV, word in parenthesis is mine )
3 (Ephesians 1:7; Romans 8:1)
4 (Romans 8:12-17; Galatians 3:26; 1 John 3:1)
5 (1 John 1:9)