Abu Huraryah (RAA) reports that the Prophet (SAW) said, “Whoever eats one day of Ramadan without a valid reason or excuse or genuine illness (acceptable in Shari’ah), shall never be able to compensate for that day even by fasting the resting of his life”. (Ahmad, Tirmizi, Abu Dawood, and Ibn Majah)
Meaning where a day of Ramadan has been lost without excuse, any number of fasts by the way of compensation will not bring back the true blessings of even one day of Ramadan.
This all is for those who keep the qadha fast. How unfortunate and misguided are those who deny the fast and do not observe it all? Fasting is one of the fundamental pillars of Islam. The Holy Prophet (SAW) has mentioned five principles of Islam. First and the foremost is the oneness of Allah and Muhammad (SAW) being a messenger of Allah and thereafter the four famous pillars : Salah, Fast, Zakat and Hajj.