What financial irregularities did Jean-Baptiste Colbert expose in Nicolas Fouquet’s accounts?

Jean-Baptiste Colbert exposed that Nicolas Fouquet, the surintendant des finances, had enriched himself through various financial operations that were conducted in an irregular manner. While these practices were not necessarily contrary to the customs of the time, Colbert denounced them to destroy Fouquet’s reputation with Louis XIV.12

Specifically, Colbert revealed that financiers and tax farmers had generated enormous profits through loans and advances made to the state treasury. By highlighting these irregularities, Colbert aimed to secure his own position as finance minister. Following Fouquet's arrest, Colbert further sought to restore the king's credit by establishing tribunals to force financiers to return some of their gains and by repudiating certain government bonds to reduce the public debt. During the subsequent trial, Colbert suppressed evidence that would have implicated Cardinal Mazarin in many of the same financial transactions.12