How soon before the end of the month can i tax my car so it starts at the beginning of the next month?

Ie can i tax it tomorrow to start on the 1st of next month?

I thought it was 2 weeks.

If you're already taxed, from the 5th of the month it's going to expire.

If you're not already taxed you can tax it from the first day of next month not more than two days in advance.

Sounds like I thought wrong.

adrian