Single sales bill of multifirm

Dear Sir, We have 4 firms in our family shop. We had created firmwise items. 1 firm having vat tin no. Can we pass single combine sales bill on the header we will print name of all the 4 firms & at footer we will give our 1 firm's vat tin no. At the end of day, our software will split sales bills & sales will goes autometicaly to particular firms by item. We are issung a single bill (combined) to customer with 4 firms name on bill header & 1 firm vat no at the footer. This type of bill is legal from the view of income tax & Mvat?