Spanish to English Bus/Financial Law: Taxation & Customs Withholdings at source

From the same list as my previous query.
I have a very low tolerance level for undefined acronyms at the best of times. I'm able to guess most of the other abbreviations in this sentence or string, but N/D has me puzzled.

"N/D a inst. estado y empr. públicas que percibe ingreso exento de imp. renta".