This probably depends on what region someone lives in, but in America, a formal letter usually ends with "Sincerely" or "Regards." 

This probably depends on what region someone lives in, but in America, a formal letter usually ends with "Sincerely" or "Regards." 

In the formal letter you should write "with my best wishes" or "regards".

You can say "sincerely." Or if it is a professional letter, such as a job application, you should thank the recipient for their time by saying "thank you for the consideration" or "thank you for the opportunity".