R.I. Gen. Laws § 44-18-26: Tax on retailer’s use of merchandise.

If a person who gives a certificate consumes or makes any storage or use of purchased property other than retention, demonstration, or display while holding it for sale in the regular course of business, the storage, use, or consumption is subject to the sales or use tax, as the case may be, as of the time the property is first stored, used, or consumed, and the cost of the property to the purchaser is the measure of the tax.