I'm sure there's an official answer to this in an IRS publication, but we have simply provided our ein# and a statement that our PTO is a 501c3 organization. If the vendor needs more than that, they probably would have asked for your determination letter when they made the initial donation.
I have a copy of what I assume is the Letter of Determination (?) from the IRS. It is about 3 pages long. When I am giving a thank you letter for donations, do I need to send a copy of this whole thing? Or is there a particular number on it for me to use? I have on there an EIN, a DLN, and an ID# that appears to be related to the Contact Person. I need to send out about 25 thank yous, and hate to think about making copies of this 3 page thing! Noone in the office knows the answer, so I'm hoping someone here does!