Person who fills out a form - single word

I decided to turn to existing forms rather than just reaching into the air for an obscure term. Here's the USCIS I-129F form, which is a government form that might be prepared by someone other than the petitioner. They call this person the preparer.

Submitter, because they just submitted the form?

-- to present (something) (optionally for a approval / review)

For example, I submit an edit here, I am the submitter.

User is another option.

How about

Responder

re•spond•er (rɪˈspɒn dər)

n. 1. a person or thing that responds.

Consider formfiller, something or someone who fills out forms. For example:

He used to be the best formfiller I ever knew. But now...

I don't have a dictionary reference for this form, but see en.wiktionary's definition of formfilling as “The filling out of forms”.