I disagree with @ZoltanB45 .
Most balance sheets maintained by a partnership are on a GAAP or book basis.
While the reporting of the capital account changed last year, to be a tax capital account, this is not the same as your outside tax basis.
If you have the K-1 from every year (kudos to you for having this), then I suggest the following:
- Hopefully you understand using excel good enough to provide assistance in determining your tax basis
- Keep in mind, this most likely is not completely accurate, since you were not provided what your gifted tax basis was at that time; but close enough. The best information you have available.
- Find your initial K-1. Hopefully there is a figure on the increase/decrease line (what is now Line L on the K-1) that reflects transferred basis. This will be your starting point. I know what I just said, but that is all you have.
- Next, for each year K-1, including your initial, adjust your tax basis for the applicable lines in Part III
- See page 3 of the K-1 instructions for some help; link below
- https://www.irs.gov/pub/irs-pdf/i1065sk1.pdf
- Once you have completed the worksheet for every year, adjust for your final K-1 for all items EXCEPT for any distributions on the final K-1.
- When entering the information for the sale (liquidation); your final distribution will be the sales price, your tax basis which you just calculated will be your cost.
- TT will then compute your overall gain or loss
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
