Yes, it is. The rule for the prostration of forgetfulness, sajdah sahw, is the same in obligatory, sunnah and voluntary prayers. A mistake that makes it wajib in an obligatory prayer makes it wajib in a sunnah or voluntary prayer too. This is stated plainly in the Hanafi work Fatawa Hindiyyah (Fatawa Alamgiri). Most Muslims in Bangladesh follow this school.
When it becomes wajib
If a wajib act of the prayer is left out by mistake, the shortfall is made good by sajdah sahw. Examples are standing up without sitting after the second rakah in a prayer of three or four rakahs, forgetting to add another surah after Surah al-Fatihah, and leaving out the qunut supplication in witr. In the Hanafi view, adding a surah to al-Fatihah is wajib in every rakah of sunnah and voluntary prayers, so sajdah sahw is needed if it is left out in any rakah of these prayers.
If a wajib act is left out deliberately, sajdah sahw does not make up for it. According to Hanafi jurists that prayer must be offered again.
What the hadith say
Abdullah ibn Buhaynah (may God be pleased with him) said the Messenger of God (peace be upon him) once stood up in the Zuhr prayer after two rakahs without sitting, and the people stood with him. At the end of the prayer, when everyone was waiting for the salam, he said the takbir while seated and made two prostrations, then gave the salam. (Bukhari, hadith 829, 1224)
The narration of Abdullah ibn Masud (may God be pleased with him) says that once, when five rakahs had been prayed at Zuhr, the Prophet made two prostrations after the salam. (Bukhari, hadith 1226)
In another hadith the Prophet said that if anyone is in doubt about how many rakahs have been prayed, they should make two prostrations while seated. (Bukhari, hadith 1232)
How it is performed
The hadith describe sajdah sahw both before and after the salam, and the imams differ on which is better. The Hanafi method is to recite the tashahhud in the final sitting and give one salam to the right, then say the takbir and make two prostrations, then sit and recite the tashahhud, the salawat and a supplication again and end the prayer with the salam to both sides. If someone makes the two prostrations before the salam, the prayer is still valid.
If mistakes in prayer happen again and again, or if it is not clear which rule one’s own case falls under, it is best to ask a reliable scholar.
বাংলায় মূল প্রতিবেদন পড়ুন · Read the original Bengali report