How To Modify the "Effective To" date for a Tax Rate

Hello All,

we recently upgrade the application to R12, I now need to modify the 'Effective To' for one of the Tax Rates. Tried through all the possible navigations (in TAX Administrator and TAX Managers responsibilities) and options but couldn't find out where exactly it can be modified.
'Effective To' date field in the TAX rate tab doesn't show the option to modify it. please refer the screenshot
This is really important from VAT tax calculation purpose, please throw some light if you would have already see this earlier.

Thanks,

Vara