Research by comparison website money.co.uk also shows that, of those who do know, 50 per cent do not know the exact date of the changes and 6 per cent think it is sometime next year.
The changes will mean the traditional tax disc no longer has to be displayed after 93 years on car windscreens, while those looking to buy or sell vehicles will no longer be able to transfer the tax.
However, for some the changes, due on October 1, will bring a welcome lifeline as a new direct debit scheme is introduced.
The scheme will allow motorists to spread the cost of road tax over 12 months, incurring a five per cent additional charge.
Website editor Hannah Maundrell said: "We fully welcome the introduction of direct debit payments, particularly for consumers who may be struggling to keep up with the soaring cost of driving.
"It will also help to eliminate the problem of people who genuinely forget to renew their tax and end up being stung with a hefty fine.
"Just because you don't have to display a tax disc doesn't mean you can get away with not paying it. This is particularly an issue if you are buying or selling a vehicle. You must ensure that you contact the DVLA and pay for the tax on your new motor before you drive it home."