New York State-Sales tax exempt organizations

Organizations that must apply:

Not-for-profit religious, charitable, educational, or other organizations (often called section 501(c)(3)) organizations)
United Nations and other international organizations
United States armed forces posts and organizations

Organizations that don't need to apply:
New York State and United States governmental entities (because they are already exempt)
Other states and political subdivisions (because they don't qualify)
Organizations that are organized and/or operated under some other New York State or federal statute that exempts them from state and/or local sales taxes

If you're granted sales tax exempt status

NYS issues Form ST-119, Exempt Organization Certificate, to you. It will contain your six-digit New York State sales tax exemption number. (Note that the nine-digit federal employer identification number issued by the Internal Revenue Service is not a sales tax exemption number.) You'll also receive Form ST-119.1, Exempt Purchase Certificate.

To make tax exempt purchases:

Complete Form ST-119.1 (This form is mailed with your exemption certificate, and is not available on our Web site. To get additional copies of this form, contact our sales tax exempt organizations unit.)
Present the completed form to the store at the time of purchase. All purchases made by an exempt organization are exempt from sales tax.
New York State and United States governmental entities that are already exempt should make exempt purchases by presenting governmental purchase orders or a letterhead.
Acceptable exempt certificate use

You may only use your exempt organization certificate to make exempt purchases on behalf of the approved organization.

An officer, member, or representative of the organization may not use the certificate to make personal purchases.
Only the organization that was issued the certificate may use it.
The exempt organization must be the purchaser and payer of record.
Misuse of your exempt organization certificate is punishable by imprisonment and a fine of up to $20,000.

To read more! New York State-Sales tax exempt organizations Source: InfoTaxSquare Business Documents Filing In All Fifty States!