أَسْتَغْفِرُ اللَّهَ رَبِّي مِنْ كُلِّ ذَنْبٍ وَأَتُوبُ إِلَيْهِ
Transliteration
Astaghfirullaha Rabbi min kulli dhanbin wa atubu ilayh
English meaning
I seek forgiveness from Allah, my Lord, for every sin and I repent to Him.
When is it recited?
Daily throughout Ramadan.
Source
Bukhari, Da'awat 3