The VAT flat rate rate scheme asks traders to pick a category that matches their trade from a list provided by HMRC. If you do not match one of the trades listed, then you can choose “Any other activity that is not listed elsewhere 12%”
Many trades have a higher percentage, including management consultancy at 14% and Computer and IT consultancy or data processing at 14.5%.
In a recent case (JJK Engineering Ltd v HMRC  UKFTT TC05351) the taxpayer argued they had incorrectly used a trade classification that was similar to their trade but not an actual match. They therefore asked to be moved to the “other activities” rate of 12%, which HMRC agreed.
The taxpayer had been paying flat rate scheme percentage of 14.5%. They asked for the correct rate of 12% to be applied backdated for four years. HMRC disagreed and the taxpayer appealed. The first tier tribunal allowed the backdating.