Expenses Type exceeded amount is not deducting TAX

HI Friends,

I have created one Expense Type for 9000 GBP. As per the Table T706B2 The Maximum Value is 8000 GBP. So when the amount exceeded system splits itself to wage types 8044 and 8644.

8044 is No Tax 8000 GBP

8644 if Non exempt amount that is 1000 GBP.

But There is no changes happened in Tax. It supposed to pose tax for 1000GBP.

I have maintained another 3000 for next month. but even that 3000 is showing exempt amount.

So can any one help me how can I maintain tax for those exceeded amount.

Thanks

Rajender