In case of audit of firm, the working partners due date is 31.10.2019( extended due date with 234A applicable for AY 2019-20). While filing the ITR as rightly stated there must be tick on the check box that the firm is liable to audit.
@ Ankush if your query related to working partner then late fee will be cancelled by CPC and fresh intimation will be issued by CPC. ( As clarified by CBDT dt 13.11.2019)