If your return was accepted and you need to remove someone from it, you would need to Amend Your Return . The amended forms will not be available until Feb 23. If there is someone else trying to file a return that you claimed on your return, they will need to print and mail their return as it will be rejected due to duplicate use of a social security number. The processing time for an amended return is greater than 16 weeks so if the other person waited to file, there return would be late.
If you have not e-filed your return yet, you would remove a dependent by revisiting the Dependents section:
If you have already filed and your return was accepted by the IRS, you will need to file an amended return. The amended forms will not be available until later this week. You can e-file the amended return. Here is a link to Amend your Return. When the 2021 Form 1040-X is available, that will show in this help article.