So our 21 plate Ford focus went in for its first mot today 1st may 24 and it failed Becuase of exhaust emissions  

 

word for word off the test certificate

(exhaust carbon monoxide content after 2nd fast idle exceeds manufactures specified limits)

 

Based on what we have been told and on the invoice. It needed a software update which when done then passed. 

so when we brought the car and has its first mot it would of always failed Becuase it would of needed this update ????

Get the software updated, if you wish, but I doubt it will do anything.

If car is over 40,000 miles consider changing the spark plugs, use good quality fuel, check air cleaner is clean and not damp, then take the car for a good run and whilst on the run, hold the revs at about 4,500 RPM for about 5 minutes (about 65MPH in 3rd gear) to give it a good blow out.

Then take it straight back back for re-test and it will pass

17 hours ago, Nathan king said:

so when we brought the car and has its first mot it would of always failed Becuase it would of needed this update ????

Maybe.  Emissions are not tested during a service.  There is absolutely no way that the driver or the service tech would know that the CO is high until it gets tested for MOT at 3 years old.

It may be that something has 'worn' over time, and needed software corrections.  Or it may be as you say, the CO was always too high from the factory.