1. Valid passports: Both the US citizen and the UK citizen will need to present their valid passports as proof of their identities and nationalities.
2. Birth certificates: Copies of the birth certificates of both the US citizen and the UK citizen will be required.
3. Proof of address: The US citizen will need to provide proof of their address in the UK. This could be in the form of a utility bill, rental agreement, or council tax bill.
4. Proof of income or financial support: The US citizen will need to provide evidence of their income or financial support to show that they are able to support themselves and their spouse in the UK. This could be in the form of payslips, bank statements, or a letter from an employer.
5. Marriage visa application form: The US citizen will need to complete a marriage visa application form (Form FLR(M)) and submit it to the UK Visas and Immigration (UKVI) along with the required supporting documents.
6. Marriage certificate: Once the marriage visa has been granted, the US citizen and UK citizen will need to obtain a marriage certificate from the local registrar's office in the UK. This certificate will be required for the US citizen to apply for further immigration status, such as indefinite leave to remain in the UK.
It is important to note that the specific requirements and procedures for obtaining a marriage visa and settling in the UK as a US citizen may change from time to time, so it is always best to check the latest guidance from the UKVI website or consult with an immigration specialist for up-to-date information.