Reply to @bachuchay: yes.. that is the requirement as part of the employment certificate for <b>most </b>assessing authorities..
You should get it according to this hierarchy:
1) Job description signed by HR -
2) or by your manager, in company Letterhead mas maganda
3) or any colleague na mas higher position sayo.
Mahina kasi ang dating ng ikaw lang ang gumawa.. dahil kahit sino pwede gumawa ng magandang job description..