The best of prayers for forgiveness is: 

► Allaahumma anta rabbi laa ilaaha illa anta, khalaqtani wa ana ‘abduka wa ana ‘ala ‘ahdika wa wa’dika ma astata’tu. A’udhu bika min sharri ma sana’tu, abu’u laka bi ni’matika ‘alayya wa abu’u laka bi dhanbi, faghfir li fa innahu laa yaghfir al-dhunuba illa anta 

► O Allaah, You are my Lord, there is no god but You. You have created me and I am Your slave and I am keeping my promise and covenant to You as much as I can. I seek refuge with You from the evil of what I do. I acknowledge Your blessing and I acknowledge my sin, so forgive me, for there is none who can forgive sin except You.


[Narrated by al-Bukhaari (6306)]