The Totvs Client must be Gross Withholding Agent (Parameter MV_AGENTE, position 3 = S and parameter MV_AGIIBB must contain the acronym of the provinces that do GI withholding).
You must fill in the Withhold GI field in the Supplier Register with content equal to S (= Yes), and the supplier must not be registered as exempt in the Company vs. Tax Zone configuration table.