Hi there, when I bought my rental property, there were a number of unpaid items by the seller (county taxes that were owed but not paid by the seller, for time periods before I owned the property). I also had an addendum to the contract price which lowered the ultimate cost for me by $2000. I assume the latter lowers the costs basis, but unsure about the former.

UNLESS the seller reimburses you , then,. County taxes you ay are treated as part of your rental pty cost basis. Correct; as your ultimate cost got lowered by $2k you need to lower your cost basis of the rental pty UNLESS the ultimate costs is points (disc points), mortgage ins premium or loan assumption fees;