Form 5405 is used to report the sale or disposal of a home if you purchased the home in 2008 and received the first time home buyers tax credit that must be repaid. You are supposed to file this form in the year you stop using that home as your main home (because you sold, moved out, converted to rental, transferred to a spouse in a divorce, etc.). Depending on the circumstances, you will owe full, partial or no repayment of the credit at that time. Then you owe no repayments in the following years.
This form is only created if you tell Turbotax that you received the credit in 2008 and that you sold or moved out of the home in 2020 (for a 2020 tax return).
If you are still living in the home, you may need to make a repayment if you forgot, but that does not require including the form.
If you moved out prior to 2020, you need to fill out a form 5405 for that year, report the sale, and calculate and repay your credit. It sounds like you can probably download just the form, fill it out, and mail it to the IRS with a check (if you owe money) to the office that sent the notice, rather than sending an entire amended tax return.
