Where articles of tangible personal property are taken in trade, or a series of trades, as a credit or part payment for similar new or used articles, the tax shall be paid on the sale price of the new or used article, less the credit allowed for the trade-in.
Ga. Comp. R. & Regs. R. 560-12-1-.34
Ga. L. 1937-38, Extra Sess., pp. 77, et seq., as amended; (Ga. Code Ann., Secs. 92-8405, 8406, 8409, 8427); Ga. L. 1951, pp. 360, 385; (Ga. Code Ann., Sec. 92-3438a).