The Days on which Fasting is prohibited

1) the two 'eed days, namely: al-fitr and al-adh.haa; as 'umar ibn al-khattaab (may allah be pleased with him) said:

((verily, the messenger of allah prohibited fasting on these two days, the day of al-fitr from ramadan and the other day on which you eat whilst carrying out your (hajj) rites)), i.e. 'eed al-adh.haa,

[transmitted by muslim]

2) the days of tashreeq, and they are the 11th, 12th and 13th days of dhul-hijjah.

the messenger of allah (peace be upon him) sent 'abdullaah ibn hudhaafah (may allah be pleased with him) around minaa saying:

((do not fast these days, for indeed they are the days for eating and drinking and remembering allah (the almighty))),

[saheeh, transmitted by ahmad]

and the ones excused from this prohibition are those who are performing the tamattu' or al-qiraan hajj, but have no means to offer the obligatory sacrifice. 

3) the menstrual and post partum bleeding days with respect to women.

the messenger of allah (peace be upon him) said:

((is it not that when she is on her menses, she does not pray nor fast? then this is the deficiency in her religion?)),

[transmitted by al-bukhaaree] 

4) the wife fasting whilst in the presence of her husband, unless she has sought his permission.

the messenger of allah (peace be upon him) said:

((a woman is not to fast whilst in the presence of her husband, except with his permission, not including (the fast of) ramadan)),

[the authenticity of this narration has been agreed upon by al-bukhaaree and muslim]