Folx is now offering letters for gender marker changes you can learn more here: https://www.folxhealth.com/library/gender-affirming-surgery-letters-101?vgo_ee=%2BIByEQbFfL2on%2FuBntHUtONz08e7h7l53kyZagSXerUXbjE%3D%3ArW2%2FQ4HkS4GM4YtZOXItARo%2B%2BtR4Qr5h
Update as of Jan 2025 per Trump executive order you can no longer update or change the gender marker listed on your passport or with the Social Security Administration.
Passports:
If you're eligible for a passport in the US you do not need to provide any documentation to use your correct gender marker or update your gender marker. If you're currently in a state that does not allow you to update your driver's license a passport can be used instead of a driver's license + SS card or birth certificate for employment verification.
How to apply: https://travel.state.gov/content/travel/en/passports/need-passport/apply-in-person.html
Selecting your gender marker: https://travel.state.gov/content/travel/en/passports/need-passport/selecting-your-gender-marker.html
Updating your Social Security information does not require any documentation to change your gender (currently only male and female offered): https://www.ssa.gov/personal-record/change-sex-identification
State laws for updating the gender marker on your driver's license/ID with links to the appropriate applications: https://www.autoinsurance.com/guide/how-to-change-gender-drivers-license/