When you enter the "cost or adjusted basis" for an item that you donate, you enter either the original amount that you paid for the item or you enter the original purchase price, as adjusted.
Why would the cost (or "basis") of an item get adjusted?
Perhaps you used the item in a business setting and depreciated it before donating it. Each dollar of depreciation is subtracted from the original cost or basis, hence, the basis is "adjusted".
If you made substantial improvements to the item before you donated it (as opposed to repairs and maintenance), then you increase the basis by adding the cost of the improvement to the original cost. Example: you added a new bathroom to a house before donating it to a qualified charity.
As noted, normal wear and tear on personal use items and normal repairs and maintenance do not adjust the basis, so for many donated items, the cost and the adjusted basis are the same.
