27 CFR 53.2 - Attachment of tax.
(b) When title passes is dependent upon the intention of the parties as gathered from the contract of sale and the attendant circumstances. In the absence of expressed intention, the legal rules of presumption followed in the jurisdiction where the sale is made govern in determining when title passes.
(d) Where a consignor (such as a manufacturer) consigns articles to a consignee (such as a dealer), retaining ownership in them until they are disposed of by the consignee, title does not pass, and the tax does not attach until sale by the consignee. Where the relationship between a manufacturer and a dealer is that of principal and agent, title does not pass, and the tax does not attach, until sale by the dealer.
(e) In the case of a lease, an installment sale, a conditional sale, or a chattel mortgage arrangement or similar arrangement creating a security interest, a proportionate part of the tax attaches to each payment. See section 4217 and §§ 53.103 and 53.104 for a limitation on the amount of tax payable on lease payments.
(f) In the case of use by the manufacturer, the tax attaches at the time the use begins.