I've been researching the VAT Optimiser & Corgi VAT Saver and IT IS TOO GOOD TO BE TRUE!
I have looked at the worked video example on the latter's website and it says that on the installation in question, 64% (no this is not a typo!) is at the reduced VAT rate of 5%. I rang them to ask how it could be so high but they said that it includes pipe insulation, 25% of the controls within the boiler (believe it or not), trvs, etc!!?
The VAT rules clearly state that if the controls are supplied as part of a whole system then the whole job becomes standard rated for VAT purposes.
So when you do get a VAT inspection, and you will at some point, you will have to repay all of the underdeclared VAT plus probably a fine too, not forgetting of course the 25% commission you have already paid them for the use of their software. So at least 125% of the VAT 'saved'!
I will be writing to HMRC. The combined adverts states over £17 million saved already so thats £17 million in unpaid VAT!
I will not be signing up for either.