We have a similar thing in Spain, where individuals have a NIF (número de identificación fiscal) — except foreigners, like me, who have a NIE (número de identificación de extrajero) — and companies have a CIF (código de identificacion fiscal), but they all amount to the same thing: a tax identificación number or code. (In fact the NIF or NIE includes a couple of letters, so strictly they are codes rather than numbers, but they still tend to translated as "numbers").

I think there are two things you could do in order to use initialisms, so that they fit in the boxes. Both would involve adding an explanatory note. One is simply to keep the Venezuelan ones, with a note explaining what they stand for and adding a literal translation of each (which could be "tax identification number" and "tax information registration", for example), or use two different English initialisms, which could be TIN and TIR respectively, again with the note explaining this.

Of course, if there is room for the full translations in the table you could use them, but they are a bit long.

It would be the first time the RIF has been called this:

"Updated copy of the Tax Information Registration (“RIF”) of the company receiving the investment"
"Doing Business in Venezuela" (p. 47; p. 53 of file).
http://www.bakermckenzie.com/files/Uploads/Documents/North A...

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Note added at 3 hrs (2014-12-06 18:54:41 GMT)
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Sorry, I meant "It WOULDN'T be the first time the RIF has been called this".

"(v)copy of the tax information registration (Registro de Información Fiscal (RIF));"
http://www.wtocenter.org.tw/SmartKMS/fileviewer?id=15028 (p. 24)