The final details of the tax basis are not available until after the closing date of the tax year. Also, a completeness check may show that no tax bill was imposed for some addresses.
It is unfortunate that you are confronted with this bill in arrears. However, the costs were incurred. The legislation offers the option of imposing the tax bill retro-actively.
Do you want to pay your tax bill in instalments? Check the payment page for more information.