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DNI = Documento Nacional de Identidad, in words a "national identity card". All Spanish citizens & residents, like me) must carry this at all times, else they risk being fined.

CIF = Cost, Insurance & Freight, used for international contracts.

However, I have my own idea that is a company identication number used by the state, much like UK cos. have to have a VAT no. of they are to issue VAT invoices.

I hope this helps. I'm sure a native will know what the abbrevioation "CIF" stands for, for certain. Google only came up with "Cost, Insurance and Freight"

NDP.

DNI stands for "Documento Nacional de Identidad"- literally "National Document of Identity". It is a small card that every Spanish citizen of legal age is obliged to have. On one side figures your photograph, your name and surnames, your signature, the period of validity and a number with eight figures and a letter at the end. On the other side figure your place and date of birth, the names of your parents, your sex, your address and a few more numbers.
When the Identity Number appears with the letter at the end it is also known as NIF (Número de Identificación Fiscal) which, for example, translators have to put on their invoices. People have NIFs; companies have CIFs.
It is usually translated into English as "Identity card" or "Identity document".

CIF stands for "Código de Identificación Fiscal" and we could say it is the Identity Card of firms. Each firm or company is obliged to have this code number which consists of a letter and eight numbers. This number must appear in all their paper work.
This is translated into English as "Fiscal Identification Code".

I hope I have been of help and good luck with your translation.