Change taxes VK11/VK12

Hi gurus,

in VK13:

Condition Type ZXXX:

Tax CL3 custom:1

Tax CL3 Mat:4

Valid from: 01.07.2008 to 31.12.2010. Tax Code: T4

I need Tax CL3 custom:1

Tax CL3 Mat:4

Valid from: 01.01.2011 to 31.12.9999. Tax Code T5 (created through FTXP).

I have created this new validity period through VK11.

However i can not asign it in VK12:

The condition is being processed in the current session-> Message no. VK104

How can i add this new validity period or system updates automatically this new data?

Thanks a lot!