Yes, donations are potentially tax deductible if the original donor is a US resident, since they are charitable donations to Pledgeling Foundation, a US 501c3. Actual deductibility will depend on whether the donor takes the standard deduction, or itemizes, and other details of their individual tax situation.

Check your local tax regulations if you are outside the US.

How do I send tax receipts to donors?

When the donation is made via API, you include the donor information in the API call. You can then set a parameter that will trigger our emailing of the tax receipt to the donor. 

US tax receipts are required for all donations over $250; you must still set the parameter to email these (this is because we can't anticipate every developer's situation).

US tax receipts are optional for amounts less than $250, but it is a best practice to send them for any donation over $5 or so.