اللَّهُمَّ اغْفِرْ لِي ذَنْبِي كُلَّهُ، دِقَّهُ وَجِلَّهُ، وَأَوَّلَهُ وَآخِرَهُ، وَعَلَانِيَتَهُ وَسِرَّهُ
What this dua means
It leaves no sin out: every kind, every time, every place.
When to read it
Say it in sujood during prayer, as the Prophet did.
Its virtue
Its completeness covers sins you remember and sins you forgot.
getsalahtime.com