Art. 57 Federal Law of 13 October 1965 on Withholding Tax (WTA)
Art. 57 LIA
The cantons shall submit to the Confederation a statement of the amounts of withholding tax they have refunded.
The Federal Tax Administration (FTA) shall review the statements from the cantons; for this purpose, it may consult all relevant documents with the cantons, districts, circles, and municipalities, and may order, in specific cases, additional investigative measures or exercise itself the investigative powers of a cantonal withholding tax office.
If the review reveals that the refund was wrongfully granted by the cantonal withholding tax office, the FTA shall provisionally order a corresponding reduction of the amount claimed by the canton in one of its subsequent statements.
After a period of three years from the end of the calendar year in which the decision of the cantonal withholding tax office became final, the FTA can only order the reduction in connection with a criminal proceeding.