Just to clear it up for anyone else. It no longer checks for insurance when taxing a car.
https://www.gov.uk/government/uploa.../Annex_A_-_consultation_responses_summary.pdf
Seems they scrapped it for this very reason, too many failed online tax applications due to insurance database not being up to date.
"The proposal will also stop 600,000 online vehicle tax applications a year
failing when the insurance details are cross-referenced with the vehicle
record. These motorists will now be able to tax using their chosen channel
rather than be forced to tax at the Post Office®"
Thanks for all the input guys.