It doesn't matter how dishonest one is. If a service provider collects money on foot of an invoice, the VAT on that invoice must be properly accounted for.Get 2 or 3 other quotes and see what they have.
If it's a "roofing company" rather than a general builder be extremely vigilant as that trade is known to be riddled with less than honest people.
Re-roofing is fairly labour intensive.It doesn't matter how dishonest one is. If a service provider collects money on foot of an invoice, the VAT on that invoice must be properly accounted for.
Beware also of the possibility of a competitor conveniently pretending for quote purposes that the two thirds rule doesn't exist, only to "remember" later on that it does.
They can ask but they won't get it, if the roofer they engage is anyway serious about the manner in which they run their business.Re-roofing is fairly labour intensive.
So maybe the poster should ask for a breakdown of the quote between materials and labour.
Then there's no dispute later