The King's Counter is a position in the royal court of the Seven Kingdoms. The position falls under the jurisdiction of the master of coin.
According to a semi-canon source, the King's Counter is the official who manages taxation in Westeros. Tax assessors and tax farmers are employed by the King's Counter.
Tyrion Lannister notes that several key offices of the royal bureaucracy are filled by Petyr Baelish's men, among them the King's Counter.