Null tags in XML

Hi,

I have few null tags in the XML file which is showing presented as below:

<TAX_CODE/>

Now in my template,

there is a group by option(group by DEVICE_ID) , then we have to put a check whether the TAX_CODE is null based on which a table is to be displayed.PFB the code:

<?for-each-group:DEVICES;./DEVICE_ID?><?if:contains(DEVICE_ID,'login')?><?if:TAX_CODE='null'?><?for-each:current-group()?>......

I have gone through the Oracle docs(Creating an RTF Template) and tried with the code

<?if:TAX_CODE and TAX_CODE=' '?> desired behavior <?end if?>