Obligatory prayers may be combined, unlike voluntary prayers.

Obligatory prayers carry a greater reward than voluntary prayers.

A small amount of drinking is permissible during a voluntary prayer, but not during an obligatory prayer. (1)

Some voluntary prayers may consist of a single rak‘ah, unlike obligatory prayers. (2)

In a voluntary prayer, it is prescribed to ask Allah for His bounty or seek His protection when reciting a verse of mercy or a verse of punishment. As for an obligatory prayer, this is permissible but not prescribed. (3)

It is permissible for an adult to pray behind a child in a voluntary prayer, but not in an obligatory prayer. The correct view, however, is that it is permissible; thus, there is no difference between them. (4)

It is permissible for one offering a voluntary prayer to pray behind one offering an obligatory prayer, but not the reverse. The sound view, however, is that it is permissible; thus, there is no difference between them. (5)

Some voluntary prayers are made up in their original form, while others are made up differently, such as the witr prayer. (6) Obligatory prayers, however, are made up in their original form, with the exception of the Friday prayer: if it is missed, it is made up as the noon prayer.

The recitation in an obligatory prayer performed at night is audible, whereas one offering a voluntary prayer at night may choose between audible and silent recitation.

According to one of the two views, covering the shoulders is obligatory in an obligatory prayer, but not in a voluntary prayer. (7)

Some voluntary prayers are waived during travel, whereas no obligatory prayer is waived.