GST no issue

A user realised after submitting their May GST return that a purchase invoice was entered without their GST number. The supplier claims they haven't paid GST and therefore didn't include the GST number. The user is seeking a solution as they cannot claim Input Tax Credit (ITC) without the correct details. The advice given suggests the supplier should amend their GSTR-1 to include the user's GST number, or the user may need to adjust their B2C reporting.