What should I do if I do not know the actual cost/adjusted basis of non-cash donations?

[mishi612]

They were clothing items I purchased a few years ago. I used It's Deductible to calculate the donation amount.

[PatriciaV]

You may estimate the original cost of the items you donated, based on similar items for the same year. For instance, if you donated four pairs of jeans, and jeans typically cost $15 that year, you would report $60 for the original cost of the donated jeans.