WM. PRESTON LANE, JR., GOVERNOR. 437

(b) Require vendors so authorized, to furnish bond
sufficient to secure prepayment of the tax and to print
upon the property sold a statement to the effect that the
tax has been paid in advance.

(c) The terms and conditions of this section shall be
inapplicable unless the vendor shall make application to
the Comptroller for the authority herein contained, and
unless the Comptroller, after hearing, shall find that the
conditions of the vendor's business are such as to render
impracticable the collection of the tax in the manner other-
wise provided under this sub-title.

268. It shall be presumed that all receipts for the sale
of tangible personal property and services mentioned in
this sub-title are subject to tax until the contrary is estab-
lished, and the burden of proving that a receipt is not
taxable hereunder shall be upon the vendor or the pur-
chaser as the case may be. Unless the vendor shall have
taken from the purchaser a certificate signed by and bear-
ing the name and address of the purchaser and the number
of his registration certificate to the effect that the prop-
erty or service was purchased for resale, the sale shall be
deemed a taxable sale of retail. The certificate herein
required shall be in such form as the Comptroller shall,
by regulation, prescribe and in case no certificate is fur-
nished or obtained prior to the time the same is consum-
mated, the tax shall apply as if the sale were made at retail.

269. In order to permit the tax imposed by this sub-title
to be paid and collected on the basis of the total sales price
on all sales made on the same occasion by the same vendor
to the same purchaser, without regard to the value of the
sales price of the separate items aggregating the total
amount of the sale, any group or association of vendors
are hereby authorized to establish appropriate rules and
regulations to provide uniform methods of adding the
average equivalent of the tax to the selling price in each
sale or transaction subject to the tax. Such rules and reg-
lations shall be valid and effective only if written approval
of the Comptroller is given thereto. Such rules and regu-
lations, if they do not involve price fixing, shall not be
deemed illegal as in restraint of trade or commerce. In
the event appropriate rules and regulations are not sub-
mitted to the Comptroller within 60 days after this sub-
title takes effect, or within a reasonable period thereafter,
fixed by the Comptroller, he shall formulate and promul-
gate appropriate rules and regulations to effectuate the