One of the unfortunate quirks of the Vehicle Excise Duty (VED) system is that you can only purchase VED for a whole month, regardless of what day of the month you tax it from. So when you taxed your car on the 28th March 2022 you paid for tax for the whole of March 2022. That means your tax expires at the end of February 2023, as this would be 12 months. The only thing you can do to avoid this is to tax your vehicle on the first day of the month.