When you’re mailing your federal return, you don’t necessarily need to attach copies of Forms 1099-B or 1099-DIV.
According to Assemble Your Return in the Instructions for Forms 1040 and 1040-SR:
Assemble any schedules and forms behind Form 1040 or 1040-SR in order of the “Attachment Sequence No.” shown in the upper-right corner of the schedule or form. If you have supporting statements, arrange them in the same order as the schedules or forms they support and attach them last. File your return, schedules, and other attachments on standard size paper. Cutting the paper may cause problems in processing your return. Don’t attach correspondence or other items unless required to do so. Attach Forms W-2 and 2439 to Form 1040 or 1040-SR. If you received a Form W-2c (a corrected Form W-2), attach your original Forms W-2 and any Forms W-2c. Attach Forms W-2G and 1099-R to Form 1040 or 1040-SR if tax was withheld.
If you have to attach Forms W-2, W-2c, W-2G, 1099-R or 2439, as referred to above, be sure to attach those to the front of Form 1040 or 1040-SR.
State return requirements vary. What state return are you filing?
