Reclassification of tax band

hi all
Wanted to ask if I could go into any MOT garage to get a UK emissions certificate ? Reason I ask is that I am looking at buying a japanese import that has been converted and registered in the UK earlier this year and has had the clocks changed from KMH to MPH but has been dumped into the higher tax band because of supposedly not having a UK emissions certification. Does this sound legit or is the dealer having me on ? It sounds plausible to me but then I nearly fell for "the oxford english dictionary has a mistake in it as they left out the word "gullible" in the new edition" (I know, pretty stupid).

Is this a bike or a car? Bikes aren't taxed on emissions so if this is what a dealer is saying, maybe you should question anything else they've said too.

sorry, should have said its a car...a 2004 smart car 599cc to be precise.