i had intended to fast the shawwal fasts but due to my monthly periods if im not able to do so....since i intended it but couldnt...will i get ajar for it? as the prophet(s.a.w) said wen one makes an intention to do good deed it is written for him asif he did it...?

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.

You will be rewarded for your intention to fast, Allaah willing. The Prophet, sallallaahu ‘alayhi wa sallam, said: “Verily, Allaah, The Exalted, has recorded the good and the evil deeds and then made it clear that he who intends to do a good deed but did not do it, Allaah records it as one complete good deed …” [Al-Bukhari and Muslim]

If you fast the six days outside of Shawwaal, then it is hoped that you will still gain the reward for fasting (the six days of Shawwaal), and not just the reward for the intention. A group of jurists held that if the person fails to fast the six days of Shawwaal in the month of Shawwaal, then he may fast them in Thul-Qa‘dah and it is hoped that he will gain their reward, especially if he failed to fast in Shawwaal for a sound excuse.

The Hanbali scholar Ibn Muflih wrote, “It is probable that the person gains the reward by fasting them in [a month] other than Shawwaal according to the opinion of some scholars which was mentioned by Al-Qurtubi, because the reward of fasting is tenfold, as highlighted in the report narrated by Thawbaan, and it was made particular to Shawwaal because it is easier for the person to observe fasting in Shawwaal as he is (still) used to fasting (right after Ramadan); so it is a religious concession and it is better for one to avail himself of religious concessions …” [Al-Furoo‘]

Ibn ‘Uthaymeen preferred this opinion. He said regarding the person who fails to fast the six days in Shawwaal, “If he fasts on those six days in [a month] other than Shawwaal with a valid excuse, then he gains the reward (of fasting them in Shawwaal). However, if he fasts them in other than Shawwaal with no excuse, this is the same as delaying them until the month expires, so he does not get the reward for fasting the six days.”

For more benefit, please refer to Fatwa 114658.

Allaah Knows best.