Answered by: Alimah Nasima Umm Hamza
What reasons can you break from a fard prayer? And sunnah prayers?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
In summary, breaking the prayer can be haram, mubah (permissible), mustahab (preferred) or wajib.
– It will be Haram without a valid excuse
– It will be Mubah if the person feared that they would lose their wealth
– It will be Mustahabb to seek completion of the prayer (rather than breaking)
– It will be Wajib for saving a life.
Also, it is wajib to break the salah if the person’s parents call for help. If they call him in a fard prayer, but it is not for help, then he should not break his prayer.
If the person is praying a nafl prayer, and the parents know he is in salah, then the salah should not be broken. However, if they do not know he is in salah and call, then the salah should be broken. 
Only Allah Knows Best.
Answered By Alimah Nasima Umm Hamza
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Ibn Abideen, Raddul Muhtaar, Volume 2, Pages 51-52