Burden of proof in inter-state transfers requires dealer declarations; failure results in deeming of sale for tax purposes. When a dealer claims an interstate movement was a non-sale transfer to another business place, agent or principal, the dealer bears the burden of proof and must furnish a prescribed declaration and evidence of despatch within the prescribed or permitted time; absent such declaration the movement is deemed to be occasioned by sale. The assessing authority may, after inquiry, accept the declaration and order that no inter State sale occurred, but reassessment or revision is allowed on discovery of new facts or contrary findings.