Fasting only once per month
Question

                Is it allowed in Islam to fast only once in a month?
Praise be to Allah.
If you mean fasting once in every month as well as fasting the entire month of 
Ramadaan, there is nothing wrong with this and this deed will be rewarded.
A man came to the Messenger of Allaah 
 (Peace & Blessings of Allaah be upon Him) asking him about Islam. The Messenger of 
Allaah 
 told him to pray five times a day. The man asked, "Do I have to do any more 
than that?" The Prophet 
 told him, "Only if you want to." The Messenger of Allaah 
 
told him that he had to fast the month of Ramadaan. . The man asked, "Do I have to do 
any more than that?" The Prophet 
 told him, "Only if you want to." The Messenger of 
Allaah 
 told him about zakaat. . The man asked, "Do I have to do any more than that?" 
The Prophet 
 told him, "Only if you want to." The man went away, saying, "By 
Allaah, I will do no more and no less than this." The Messenger of Allaah 
 said, "He 
will be successful, if he is telling the truth." (Reported by al-Bukhaari, 2481).