if this was a publicly traded partnership you should have received a supplemental schedule for determining your tax basis and the amount of any ordinary income recapture which increases tax basis for capital gain/loss purposes.
example
sales price $50 tax basis before ordinary income recapturer (sometimes referred to as section 751) $30 = $20 gain. $40 ordinary income recapture is reported in supplemental schedule and usually on line 20AB of k-1
your tax basis is now $70 so you have a $20 capital loss and $40 of ordinary income.
for a private partnership one should assume that schedule L is on the tax basis as required by the IRS (no guarantee) so tax basis is beginning capital + capital contributed + current year income or - current year loss + other increase - other decrease. selling price is line 19 which hopefully is the same as schedule L line for withdrawals and distributions. and ordinary income recapture, if any, should be note on k-1 or a supplement.
