Section 8. (a) It shall be presumed that all gross receipts of a vendor from the sale of services or tangible personal property are from sales subject to tax until the contrary is established. The burden of proving that a sale of services or tangible personal property by any vendor is not a sale at retail shall be upon such vendor unless he takes from the purchaser a certificate to the effect that the service or property is purchased for resale, and such certificate is received and made available to the commissioner not later than sixty days from the date of notice from the commissioner to produce such certificate. Where a certificate is received within the foregoing time limit but is deficient in some material manner and where such deficiency is thereafter removed, also within the sixty day period, the receipt of such certificate shall be deemed to have satisfied the foregoing time requirement.

(b) The certificate shall relieve the vendor from the burden of proof only if taken in good faith from a person who is engaged in the business of selling services or tangible personal property of the same kind as the services or property sold and who holds the registration as provided for in section seven and who, at the time of purchasing the service or tangible personal property, intends to sell the service or property in a sale at retail in the regular course of business or is unable to ascertain at the time of purchase whether the service or property will be sold or will be used for some other purpose.

(c) The certificate shall be signed by and bear the name and address of the purchaser and the number of his registration, and shall indicate the general character of the service or tangible personal property sold by the purchaser in the regular course of business. The certificate shall be in such form as the commissioner may prescribe.

(d) If a purchaser who gives a certificate makes any use of the service or property other than retention, demonstration or display while holding it for sale in the regular course of business, the use shall be deemed a retail sale by the purchaser as of the time the service or property is first used by him, and the cost of the service or property to him shall be deemed the gross receipts from such retail sale. If the sole use of the property other than retention, demonstration or display in the regular course of business is the rental of the property while holding it for sale, the purchaser may elect to include in his gross receipts the amount of the rental charge rather than the cost of the property to him.

(e) If the tangible personal property is purchased by a person who will use the property in a manner which exempts it from the tax imposed by this chapter, he may give an exempt use certificate to the vendor, certifying that the property being purchased will be so used. The burden of proving that a sale of tangible personal property by any vendor is exempt under this chapter shall be upon such vendor unless he takes from the purchaser a certificate to the effect that the property will be used in an exempt manner.

(f) The exempt use certificate shall relieve the vendor from the burden of proof only if taken in good faith for the purchase of property from a person who is engaged in an activity described in paragraph (r) or (s) of section six, and who, at the time of purchasing the tangible personal property, intends to use the property in an exempt manner or is unable to ascertain at the time of purchase whether the property will be used in an exempt manner or will be used for some other purpose, and such certificate is received and made available to the commissioner not later than sixty days from the date of notice from the commissioner to produce such certificate. Where a certificate is received within the foregoing time limit but is deficient in some material manner, and where such deficiency is thereafter removed, also within the sixty day limit, the receipt of such certificate shall be deemed to have satisfied the foregoing time requirement.

(g) The exempt use certificate shall be signed by and bear the name and address of the purchaser and the number of his registration, if any, give a description of the property being purchased, certify the exempt use to which the property will be applied and be in such form as the commissioner may prescribe.

(h) If a purchaser who gives an exempt use certificate makes any use of the property other than the one therein certified, the use shall be deemed a retail sale by the purchaser as of the time the property is first so used and the cost of the property to him shall be deemed the gross receipts from such retail sale.

(i) The commissioner may promulgate regulations determining which services shall be deemed purchased for resale under this section, containing provisions for the issuance of certificates to the effect that services are purchased for resale.