I had the same question. Here is an answer I got from an TurboTax Expert via Premier Live.
"For Line J, in short, it is not necessary to report your basis on your tax return until when you sell your share of the partnership or when the distributions from partnership exceed your basis. Taxpayer is responsible for tracking the basis and reporting the basis when shares of partnership are sold. That is the reason TurboTax did not ask for that information." For more details, please refer to this IRS instruction on Schedule K-1 (Form 1065), specifically relating to Item J. <a rel="nofollow" target="_blank" href="
https://www.irs.gov/instructions/i1065sk1">https://www.irs.gov/instructions/i1065sk1</a>
For Line L, it is for partnership to track partners' internal basis. This is not a required entry for tax payer/partner. For more details, please see IRS instruction for Form 1065: <a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/i1065.pdf">https://www.irs.gov/pub/irs-pdf/i1065.pdf</a> (Search for K-1, Item L)."
