For donations of $250 or more, a donor does need a written acknowledgement from UConn to take a deduction on their tax return. The Foundation can assist in issuing acknowledgements. For donations of less than $250, a written acknowledgement is not required, although donors may like to receive a letter to acknowledge their donation.
If a donation involves something other than cash (e.g., art, science equipment), then additional acknowledgment rules come into play. My office has issued guidance re: non-cash gifts, located here.
You are also welcome to reach out to Christopher Cipriani here for guidance if a donor approaches you with a non-cash gift.