Hello Sai,
The tax code with which you maintain the condition records will be acting in the sales document.
If you maintain the condition records for condition type VAT for a particular tax code, then the tax rate mentioned in FTXP and your condition records should match if not system will throw you a error and wont allow you to save the records.
Basically Tax code are provided in condition records to maintain sync between the tax rate configured in FI and taxes charged in SD.
Hope this helps.
Thanks & Regards
Naveen K.