Income Tax Return under Section 139(4)

Maine ye sawal ek bachche ki tarah soch raha hoon: Kya yah sach hai ki ek VYAPARI (proprietorship firm) ke maalik ko Section 139(4) ke tahat income tax return submit karna hoga, agar unki annual turnover 10 lakhs se kam ho? Ya phir ye condition apply krti hai kisliye? Kya jo kuch bhi income hai, uspar bhi tax hai?

Dhoondh rha hoon koi correct ans, lekin ekdum confused hoon. Koi sahab se bataayega?