1) April 15 participant 2) April 15th figure 3) April form submitter 4) Certain clerk 5) Certain clerk at work 6) Certain office worker 7) Clerk 8) Clerk at work 9) Clerk, at times 10) Folder filler 11) Form 1040 submitter 12) Form 1040 user 13) Form-1040 remitter 14) IRS customer 15) Litigant 16) Litigator Found on https://www.crosswordclues.com/clue/filer