In some applications, websites, and certificate forms, both first name and last name fields are mandatory. However, I officially have only a single name in all my documents.

What is the correct and commonly accepted way to fill the last name field in such cases?

Should I:

• Leave it blank

• Repeat the same name

• Use "NA"

• Use a dot (.)

I want to avoid issues in certificates and official records later.

Thank you in advance for your help.