Vehicles that have reached the end of their usefulness must be scrapped at an authorised treatment facility (ATF). This is usually free.
If your vehicle has been damaged and written-off by your insurance company, you’ll usually hand it over to them to dispose of.
If you’re taking parts to repair or restore another vehicle, you’ll have to make a SORN (Statutory Off Road Declaration) or keep taxing it until you take it to an ATF. ATFs are allowed to charge for handling and disposing of vehicles that are significantly incomplete.