Section 19.185 - Testing scale tanks for accuracy(a) A proprietor who uses a scale tank for tax determination must ensure the accuracy of the scale through periodic testing. Testing of the scale must be conducted at least every 6 months and whenever the scale is adjusted or repaired.(b) A proprietor also must test, at least once a month, the gallonage represented to be in a scale tank against the gallonage indicated by volumetric determination of the contents of the tank. However, if the scale is not used during a month, it is only necessary to verify against the volumetric determination when the scale is next used. The proprietor must make the volumetric determination in accordance part 30 of this chapter. If the variation exceeds 0.5 percent of the quantity shown in the tank, the proprietor must take appropriate action to verify the accuracy of the scale.(c) If the appropriate TTB officer determines that a scale may be inaccurate, the proprietor must test the accuracy of the scale.26 U.S.C. 5006 , 5204 , 5505