Alex Hughes Aug 24, 2012:

This construction is actually very common in Spanish legal documents. For example, "Estas condiciones generales no comprenden ni la forma de pago ni las cantidades a cobrar". This type of construction can be traslated as, "These general conditions do not cover the method of payment or the amounts to be collected". The first "not" in the translation handles the "no" and the two "ni"'s in the source text. Although you could probably use "nor" it isn't really necessary.

Rosa Paredes Aug 24, 2012:

I find it troubling that three answers have been provided, yet nobody has addressed the fact that the sentence is badly written. The preposition "a" is totally out of place in "no comprende ni a los datos relativos a los Regimenes Especiales", what about de "ni" which presupposes other data not mentioned in the little context provided.
"ni a" has no place in the sentence.
IMO there isn't enough information to provide an answer.