what kind of business return? only if you are amending your 1040 would you use 1040-X and that is primarily for schedules C or E (page 1) or form 4835 or schedule F. To amend partnerships - form 1065, s-corporation 1120-s trusts 1041 with the amended box checked. C corporations -1120X. Amended s-corps- partnerships and trusts would probably require amending your 1040. under conditions even amended a C-corp may require amending your 1040
to amend 1040open return and select the amended link.