The taxpayers those who cannot file GSTR 4 are:
1) Non-resident taxable individuals
2) The taxpayers who are responsible for collecting TCS
3) The taxpayers who are responsible for collecting TDS
4) Input service provider
5) Suppliers of OIDAR
6) Compounding taxable person
Apart from the above entities, all the taxpayers opting for composition scheme can file GSTR 4.