If your are filng tax any income within usa or out side usa , need to include in your tax filing. It does not matter in which form you made it. Even  you exchage a your old car and you gain on it, by rule you have to pay gain on it.  It does not matte whether he got receipt or not, he is not gaining filing tax, there is nothing withdrawn but he owes to government.  If he has deposited to bank that may be taken as proof of his income.
So you saying if you work on cash , you do not need to file a tax ? You need W_2 form to file tax? is that you suggesting? He must have some personal records, did you read all or part of it publication 17? Can you give me the page number it says he can not file tax because work on cash and no receipt for it?  Well I accept your challage on it, and I will prove that I am 110% right and he can file tax and he should file tax because he is doing CPT. But you wrote this and that is what your level is and you see others the same "

 You are a low class jhapali which the whole nation hates and will always avoid; afterall what can I expect from you filth y swine?

maac0ikhane  talaai jhaapaali le ke bigarideko chha , tero baaule ghus khaayo ki khaaen? If not that is good and sorry to write this, but he did then  you are  another Bas****d.
साठ्ठा किन तलाई ठुलो हुन पर्या , लिडे पन को पनि हद हुन्छ ।
क्यास मा काम गर्नेले mostly भर्दैनन तर उस्लाई चाहियो तेसैले भर्छ र मिल्छ । एस्को फैस्लामा हारिस भने के गर्छस ? मुला जिद्दिको पनि हद हुन्छ , त्यो पैसा फिर्ता लिना लाई मात्रै भरिदैन ट्यक्स ।