I received a late Schedule K-1 (Form 1065) and I am now trying to figure out what data to enter for a partial sale of the partnership since I also received a 1099-B which reported the capital gain on form 8949. Do I actually enter it again as part of the entry of the K-1 into TurboTax? It seems like that would be a double entry for the same capital gain.
Yes, you should enter the sale information only once. Normally, it's best to enter the information under the Schedule K-1 section. This allows TurboTax to use your historical basis and release any passive losses that may have been carried forward.
However, since you did not liquidate your ownership interest, entering Form 1099-B may be better for your situation.