reciting Surah Iklhas recited 200 times daily gets forgiveness of 50 years of sin is there any authentic hadith on that matter

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

There are many Ahaadeeth reported  in the same meaning about the virtues of reciting Soorah Al-Ikhlaas (Quran: 112); however, scholars of Hadeeth classified them as weak.

For instance, As-Suyooti said: "Ibn ‘Adiyy and Al-Bayhaqi reported that Anas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: 'If anyone recites Soorah Al-Ikhlaas two hundred times, then his sins over fifty years will be forgiven, provided that four things are avoided; bloodshed, usurping people’s wealth unlawfully, adultery/fornication, and consuming forbidden drinks.'” [Ad-Durr Al-Manthoor]

Ash-Shawkaani wrote, “Ibn Adh-Dhurays, Al-Bazzaar, and Al-Bayhaqi reported that Anas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: “If anyone recites Soorah Al-Ikhlaas two hundred times, his sins committed over two hundred years will be forgiven him.” Al-Bazzaar commented on the Hadeeth, “As far as we know, nobody narrated this Hadeeth on the authority of Anas except Al-Hasan ibn Abi Ja‘far and Al-Aghlab ibn Tameem, and both of them have a similar degree of poor memory.” [Fat-h Al-Qadeer]

Allaah Knows best.