Dua for Forgiveness from the Quran and Sunnah
The best dua for forgiveness is Sayyidul Istighfar, the master of seeking forgiveness, which begins "Allahumma anta rabbi la ilaha illa anta." The Quran and Sunnah also teach the duas of Adam and Yunus (peace be upon them). Allah promises to forgive all sins for those who turn back to Him sincerely.