A bit of a spotlight on this KB. I wasn’t aware of for some time and now it is included in AX2012R3CU9.
Problem was that each line insert/update/delete caused a tax calculation. This was more prominent when importing large journals (several thousand lines).
The solution Microsoft provides in this KB is a technical solution. It gives you the ability to ignore tax calculations if you wanted to do it while importing (via AIF or custom code).
I have written something previously that discusses this.
Note: This new field is not part of the DIXF journal entity.
Here is a work around. Because the Fields in the query are set to Dynamic=No. Lets add it ourselves
Right click and add the field.
Refresh the target entity by either deleting and creating again. Or re generating the mapping.
Below I did not add a new field to the DMF staging table but you probably should to do it properly. I am just illustrating an idea.