Agreed – it’s normal to be continuously insured and taxed, which is the situation for me even though they renew at completely different times (and the insurance is part way through the month). You’ll always be insured when you come to renew the tax. I can’t see why it would be a problem, there’s no particular reason why they need to be the same day, and a day difference isn’t really any different to 6 months difference which is what mine now is (insurance renewal now on the date I got this car as I got a new policy, but it came with 6 months tax, from before the rules changed).