I saw everywhere Deputy CIO (Deputy Chief Information Officer), but how do I prove it? Could you advise me the source (with IT positions) I may use as a reference? HR department uses CIO Deputy, but I suggest it is wrong.
Searching the Google Books corpus can give a reasonable picture of how words are used in printed works. Querying for deputy CIO and CIO deputy in a case-insensitive search to yield both titles and job designations, you get this NGram:
This doesn’t mean that CIO deputy has never appeared in printed sources, but that a query could not find at least 40 hits.
To narrow down the results, you might try an Elephind search, which queries a number of collections of scanned newspapers. A query for CIO Deputy yields 11 hits, all of which are OCR errors for "ex-officio deputy" because the software couldn't handle the ffi ligature.
These results should convince your HR department. When it comes to language usage, an argument from silence should always win.