Ruling on writing (S) or (SAWS) etc
Question

                Is it permissible to write (S) or (SAWS) etc when mentioning the Prophet SAWS (peace and blessings of Allaah be upon him), instead of writing out the blessing in full?.
Praise be to Allah.What is prescribed is 
      to write “salla Allaahu ‘alayhi wa salaam (May Allaah send 
      blessings and peace upon him)” in full, and not to write it in abbreviated 
      form, such as writing (S) or (SAWS) etc. 

    Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) 
    said: 
As it is prescribed to 
    send blessings upon the Prophet (peace and blessings of Allaah be upon him) 
    in prayer when saying the tashahhud, and it is prescribed when giving 
    khutbahs, saying du’aa’ and praying for forgiveness, and after the adhaan, 
    and when entering and exiting the mosque, and when mentioning him in other 
    circumstances, so it is more important to do so when writing his name in a 
    book, letter, article and so on. So it is prescribed to write the blessing 
    in full so as to fulfil the command that Allaah has given to us, and so that 
    the reader will remember to say the blessing when he reads it. So we should 
    not write the blessing on the Prophet (peace and blessings of Allaah be upon 
    him) in short form such as writing (S) or (SAWS) etc, or other forms that 
    some writers use, because that is going against the command of Allaah in His 
    Book, where He says (interpretation of the meaning): 
“Send your Salaah on 
    (ask Allaah to bless) him (Muhammad), and (you should) greet (salute) him 
    with the Islamic way of greeting (salutation, i.e. As‑Salaamu ‘Alaykum)”

    [al-Ahzaab 33:56]
And that (writing it in abbreviated form) does not serve 
    that purpose and is devoid of the virtue of writing “salla Allaahu 
    ‘alayhi wa salaam (May Allaah send blessings and peace upon him)” in 
    full. Moreover the reader may not take notice of it and may not understand 
    what is meant by it. It should also be noted that the symbol used for it is 
    regarded as disapproved by the scholars, who warned against it.