It depends on inhouse SOP.if formats are having prepared by, checked by and approved by signatures in the footer of page then the form cannot be used.but if the format is prepared without any signatures then it can be used.for example: if sop is prepared on 10/05/2020 ,the same sign.and date shall be on formats also.the sop which is obsolete is having different sign and date. For example : 09/05/2018.this is the main reason why the formats of obsolete sop cannot be used with new revised SOP.