Export at confessional rate of .1%

A dealer has supplied goods to merchant exporter at .1% as per gst notification no. 41/ 2017 but merchant exporter didn't exported the goods within 90days. In that case dealer has to pay full rate of tax. My query is how he will pay difference tax ..just increase his tax liability in 3b. As invoices are already filed in gstr 1...what legal action can he do against merchant exporter