Do composition dealers need to disclose exempt supplies like normal dealer? Because in GSTR 2, the table "Supplies received from composition taxable person and other exempt/Nil rated/Non-GST supplies received" is for disclosing exempt purchases. This table is missing from GSTR 4.
In your views, invoice is required. But for exempt supplies, bill of supply is made.
In section 9, "central tax...shall be paid by...". And as per notifications, levy is exempted, so no tax is there.
And in section 31, there is "who is liable to pay... issue an invoice". Its only Invoice, not including Bill of supply, and liable to pay. The person will be liable if there is tax, as you can see it is exempted by notification.
These are my reasoning, if you are satisfied.
Let's have further discussion to reach a conclusion. Others may also join. After all we'll all learn.