Investigate carefully as this is a very tricky area. If you are a 501(c) organization, then you are required to make your last 3 tax returns available to anyone who asks. Failure to provide the forms is punishable by a fine of $20 per day.
Note, if you make the forms "widely available" by publishing them on a website or GuideStar, then you can simply direct the requestor to the site.
More info can be found at
www.irs.gov/charities/article/0,,id=96430,00.html#1
Now for the question regarding if you a legitimate non-profit (i.e., are you a 501(c) charity - probably a 501(c)(3)?). You'll want to contact the IRS and explore that.
IRS Exempt Organization customer service: 1-877-829-5500.
Hours: 8:00am - 9:30pm EST Monday-Friday.
Here is a link to a previous post about some publications that might also help.
IRS Publications for Tax-Exempt Orgs