How does one prove they're not married?

In the United States, at least, producing a copy of last year's income tax
return, showing 'single' filing status, ought to be sufficient.

so i go down and get a blank 10-40 form, fill it out with all my info and
some numbers, check the single box, copy it, copy it again so it looks more
'official', and voila....

im sure theres a better way.

randy