18:57 Nov 24, 2010
If you do a phrase search in google you will get the following:
business industry classification code - 4,990 results
business activity code - 23,800 results
business classification code - 26,700 results
It seems that business industry classification code is predominantly used in New Zealand and isn't as common.
I went with business activity code because it is the most precise. There isn't anything necessarily wrong with business classification code, but to me it is a little ambiguous, i.e., it could relate to the company's size, organizational structure, etc. With business activity code there isn't any question that it is indicating what the company does.
That's just my $.02 though ;)
I hope it helps! | 
The translation workplace 
peer agreement (net): +1
