Answered by Ustadh Tabraze Azam
Question: If one makes an intention to offer expiatory fast for a transgression committed in Ramadan is it valid before fajr ?
Also, one or two hours before fajr if one is worried due to misgivings (waswasa) that his intention wasn’t correct, is it ok if he says the intention on the tongue ?
If one ate and drank in Ramadan in different days but in the same month is one expiatory fast sufficient ?Answer: Assalamu alaikum wa rahmatullahi wa barakatuh,
I pray that you are in the best of health and faith, insha’Allah.
 It is a condition for the validity of the expiatory fast (kaffarah) or make up (qada’) fast that you make the intention before dawn (fajr). The intention is to simply know what you are doing tomorrow. Ignore misgivings.
 One expiation is sufficient. However, you must also make up the days in which you invalidated the fast. See: Must I Fast 180 Days as Expiation for 3 Broken Fasts?
And Allah alone gives success.
Checked & Approved by Faraz Rabbani