Need to amend filing status from single to head of household

Today I amended my filing status from single to head of household .  This was because my adult son wanted to get a stimulus check and filed a return this year although he has no income.  I have always supported him and claimed him as a dependent.  In order to pay my taxes on time I filed as single on May 13.  I amended the 1040 SR today and my Intuit record show that the form was accepted.  BUT I have a message from Turbo Tax saying I need to submit all the forms through the mail.  What is correct?  Do I have to spend money to send all these forms to IRS certified mail?  Thanks,