Re Error message on importing Items list

I am receiving error message "The Taxable setting in tax code NCG has been changed. This can not be imported".

The client's inventory is approx 14999 long, I have tried bringing the list in with and without editing to remove hidden items. The above enter message received without making changes to list.

The client file is not a clean one and been experience issues with Reckon POS to Reckon Premier over the last few weeks file size 555000

Has anyone ever experienced this problem before - help requested as I need to put new file in on the 1/7