Are the remembrances (dhikr) after prayer said before or after the Sunnah prayer?

The remembrances (adhkar) of prayer are not obligatory. They are recited after concluding the prayer with salutations (salam) and before performing the supererogatory (Sunnah Ratibah) prayer, as indicated by authentic hadiths. In Sahih Al-Bukhari, Ibn Abbas (may Allah be pleased with them both) said: "I used to know that the Prophet's prayer had ended by the sound of the takbir (Allahu Akbar)." And in Sahih Muslim, Thawban (may Allah be pleased with him) said: "When the Messenger of Allah (peace be upon him) finished his prayer, he would seek forgiveness three times and say: 'Allahumma Antas-Salam wa minkas-salam tabarakta ya Dhal-Jalali wal-Ikram' (O Allah, You are As-Salam, and from You comes peace. Blessed are You, O Possessor of Majesty and Honor)." The meaning of "finished his prayer" is that he had concluded it with salutations.