There are multiple ways to handle this. I suggest you use the K-1 as all the information on the K-1 needs to be reported, and you will need to allocate between capital gain/loss and ordinary gain/loss. The information on the 1099-B is reported to the IRS, so in order for your tax return to match IRS records, enter the 1099-B, but use a cost basis that is equal to the proceeds so that you have a gain/loss of $0.