Cmp03 regarding stock declaration for composition under gst

tax payable only when stock purchases are from unregistered dealer

my client was registered in Punjab VAT under composition scheme and now again he opts composition scheme. is he liable to file the CMP 03
and let me know one thing more as my client was registered earlier under composition scheme so he didn't receive any input tax credit than how to fill form purchases including VAT or Purchase and VAT separately.