Short answer
No. A convert owes no prayers, fasts or zakat for the time before accepting Islam. Obligations begin from the moment of the shahada. All four schools agree on this.
Prayers, fasts and zakat are not owed for any time before Islam. If a person accepts Islam during a Ramadan day, he holds back from food for the rest of that day out of respect, fasts the remaining days, and does not make up that day or the earlier days. A prayer whose time is still running when he accepts Islam is owed.
The four schools agree on this.
Explanation
Acts of worship become due on a Muslim. Before your shahada you were not addressed with them in a way that leaves a debt, and the Quran promises that what came before is forgiven. So there is no list of years of qada (make up) prayers for a convert, and no back zakat. The four schools agree on this.
What does start straight away:
- The current prayer. If you take shahada at 2 pm, Zuhr is still in its time, so pray it once you have learnt how or as best you can.
- Ramadan. Fast the days left in the month. In the Hanafi school, if you become Muslim during a Ramadan day, stop eating for the rest of that day and do not make it up.
- Zakat. Your zakat year begins when you are Muslim and own the nisab. The first zakat is due one lunar year later.
A different case is the convert who accepted Islam months ago but did not pray because nobody taught them. Hanafi scholars treat prayers missed after the shahada as owed once you live in a place where you could have learnt about them, so start praying now and ask a local scholar how to plan any make up. Our qada calculator helps you count and schedule them.
Do not let the learning curve stop you. Pray in the way you know while you learn the rest. See how to pray.
The evidence
Quran, Surah Al-Anfaal 8:38
قُل لِّلَّذِينَ كَفَرُوٓا۟ إِن يَنتَهُوا۟ يُغْفَرْ لَهُم مَّا قَدْ سَلَفَ وَإِن يَعُودُوا۟ فَقَدْ مَضَتْ سُنَّتُ ٱلْأَوَّلِينَ ﴿٣٨﴾
Say to those who have disbelieved [that] if they cease, what has previously occurred will be forgiven for them. But if they return [to hostility] - then the precedent of the former [rebellious] peoples has already taken place.
What came before Islam is forgiven, so worship missed in that time is not owed.
Sahih Muslim 121
Sahih... أما علمت أن الإسلام يهدم ما كان قبله ...
"Did you not know that Islam wipes out what came before it?"
Islam clears what came before, including missed worship.
Where the ruling is recorded
- al-Hidaya, Kitab al-Sawm, the chapter on what makes fasting obligatory, the convert in Ramadan. A disbeliever who accepts Islam in Ramadan holds back for the rest of the day and makes up neither that day nor the days before.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, Bab Qada al-Fawa'it. Prayers before Islam are not owed; discusses the convert who did not know prayer was obligatory.
This answer is pending review by the scholars on our team. 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.