To suspend temporarily the duty on 5,5-bis[(y,w-perfluoroC4-20alkylthio)methyl]-2-hydroxy-2-oxo -1,3,2-dioxaphosphorinane, ammonium salt and 2,2-bis[(y,w-perfluoroC4-20alkylthio)methyl]-3-hydroxy proply phosphate, di-ammonium salt and Di-[2,2-bis[(y,w-perfluoroC4-20alkylthio)methyl]]-3-hydroxy proply phosphate, ammonium salt and 2,2-bis[(y,w-perfluoroC4-20alkylthio)methyl]-1,3-di-(dihydro genphosphate)-propane, tetra-ammonium salt.