Official answer: as a monotributista you should be issuing facturas for everything you do; and the ones that exceed $43,010 ARS must include the person's info and CUIT/L.
That being said, if you're working en negro here (or abroad) and are simply wanting to keep AFIP off your back, paying the aportes is probably the most important; I've personally never heard of anyone that paid the aportes and didn't bother to issue the facturas having trouble, only people that received a transferencia in excess of $43,010 and not being in a registered dependency relationship/monotributista/sole proprietor then having their accounts frozen to bring them in compliance with the financial institution's KYC rules.
Again, not an accountant nor a lawyer, but the smart thing to do is ensure that whatever category your registered spending falls in to annually can lines up with the aportes you pay, and to emit facturas whenever possible.
To check what AFIP knows about your spending sign in to your account and then click on the Nuestra Parte tab, it will show you the total money you've spent via debit, credit, and facturas issued to you as a customer. If the amount is more than the category you're paying aportes for, bring it in line so you decrease your chances of having problems later.