Spanish to English Medical Medical: Health Care Cash receipt for a Medical Centre in El Salvador

I am in the process of translating for a friend a 5 medical invoices from the country El salvador, by the way of her father's illness.
One of the invoices, has a little box in the left side of the top of the page with the following:
No.
NIT.: 0614-231075-003-09
NRC.: 426-0

Anybody knows the meaning of those letters in hospitals in El Salvador??
My friend has no idea, her dad died there 6 months ago and she is trying to collect the money from the insurance. I am just trying to help her.


Thank you so much,
Mariu