Jehoshaphat was the royal recorder (literally a "rememberer") of Israel during the reigns of David and Solomon. He is among other important advisers and high officials of David listed in the Book of Samuel and Chronicles and later in the list for Solomon in the Book of Kings
Jehosphat was the son of Ahilud. He may have been the brother of Baana, a district governor during the reign of Solomon (if Ahilud, the name given for the father of both men, is the same father). He was a "recorder" for both David and Solomon. While the exact function of his role was unknown, as the "recorder" or "remember" he was responsible for some sort of royal record keeping.
He is listed among other higher officials in the Israelite monarchy and so would have been a close adviser to both Kings. Therefore, he had a very important role in the government of Israel. However, the role of recorder is distinct from that of "secretary" (which there were multiple). After the death of David, Solomon retained Jehoshaphat was his recorder.
While nothing is known about Jehosphat, his role in the bureaucracy of Israel and his inclusion in the list of top officials indicated he had an important impact on the governance of Israel.