Short answer
Leaving a Ramadan fast without a valid excuse is a major sin. You must repent and make up every day you missed, one day for each. In the Hanafi school there is no kaffarah for a day you never started fasting. Someone who denies that fasting Ramadan is obligatory has left Islam.
Fasting Ramadan is fard on every sane, adult Muslim who is not excused. Leaving it without excuse is a major sin requiring tawbah and one day of qada for each day missed. Kaffarah is only for breaking a Ramadan fast that was already begun. Eating openly in public in Ramadan without an excuse is a further sin.
The four schools agree on this.
Explanation
Fasting Ramadan is one of the five pillars of Islam. Allah says that fasting has been decreed for you as it was decreed for those before you. A Muslim who is adult, sane, healthy and at home has no choice to skip it.
If you missed days without a reason:
- Repent sincerely: regret it, stop, and resolve not to return to it.
- Make up every day, one fast for each day missed, as soon as you can. They do not have to be in a row. See when to make up missed fasts.
- If it was over several years, count the days. The qada calculator can help.
- Do not pay money instead: fidya is only for those who can never fast.
Kaffarah. In the Hanafi school, kaffarah of sixty days is for someone who began a Ramadan fast and then broke it on purpose by eating, drinking or intercourse. A day you never started fasting has no kaffarah, but it is not a lighter sin: you deliberately left a pillar of Islam. The four schools agree that every missed day must be made up. See breaking the fast on purpose.
Denying and neglecting. Someone who believes fasting is obligatory but is lazy or weak is a sinful Muslim. Someone who denies that fasting Ramadan is obligatory at all has left Islam, since every Muslim knows it is a duty. Eating openly in public in Ramadan without an excuse is another sin, because it shows disrespect for the month.
If you are struggling, start small: fast tomorrow, and the next day. Allah accepts the one who turns back to Him.
The evidence
Quran, Surah Al-Baqara 2:183
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ كُتِبَ عَلَيْكُمُ ٱلصِّيَامُ كَمَا كُتِبَ عَلَى ٱلَّذِينَ مِن قَبْلِكُمْ لَعَلَّكُمْ تَتَّقُونَ ﴿١٨٣﴾
O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous -
Fasting Ramadan is an obligation on every believer.
Sahih al-Bukhari 8
Sahih... وإيتاء الزكاة والحج وصوم رمضان ...
"Islam is built on five: the testimony, prayer, giving zakat, Hajj and fasting Ramadan."
Fasting Ramadan is one of the pillars of Islam.
Where the ruling is recorded
- al-Hidaya, Kitab al-Sawm, chapter on what requires qada and kaffarah. Kaffarah is for deliberately breaking a Ramadan fast; other cases require qada only.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Sawm, opening section. Fasting Ramadan is fard, and whoever denies it has left Islam.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.