Is it obligatory to read Qur'aan with the rules of Tajweed?

Praise be to Allah.

The correct view is that reading Qur'aan with the rules of tajweed is not obligatory; tajweed is only a means of making one's recitation more beautiful.

If a person reads and pronounces the letters clearly with the vowels as marked, then this is sufficient.

With regard to the verse in which Allah, may He be exalted, says:

{أَوْ زِدْ عَلَيْهِ وَرَتِّلِ الْقُرْآنَ تَرْتِيلًا}

'Translation' {and recite the Quran (aloud) in a slow, (pleasant tone and) style} [al-Muzzammil:4], that does not refer to tajweed; rather what is meant is to read it at a measured pace. (End quote, Shaykh Muhammad ibn 'Uthaymeen (may Allah have mercy on him), Liqaa'aat al-Baab al-Maftooh [1/177]).