Baking soda is zero rated.
HMRC has confirmed it will treat supplies of bicarbonate of soda as zero rated when sold in small tubs as a baking ingredient. This follows the decision of the First-tier Tribunal in Phoenix Foods Ltd(TC6296) which held that, based on the packaging and placements by the supermarkets in their baking sections, bicarbonate of soda was used primarily as a baking ingredient and therefore should be zero rated.
Supplies of bicarbonate of soda that are sold in larger, industrial-sized quantities, or marketed for non-culinary purposes, remain standard rated.
Repayment claims may be made, subject to the statutory four-year time limit.
RCB 8/2018 here.