Greetings,
Generally the cost and holding period of the partner are used by the partnership for any stock contributed to the partnership by a partner.
You may or may not be aware of the rules that will require any appreciation prior to the contribution to be taxable to the contributing partner upon disposition of the stock. The contributed assets have built-in gain (BIG), which eventually will be subject to income tax when realized by the partnership; but under Sec. 704(c), this BIG is taxed to the contributor.
If you have not already had conversations with a tax practitioner experienced with investment partnerships please consider that the time and effort spent may avoid unintended tax consequences in the future.
Best regards.
Enrolled Agent
I have prepared individual, trust, partnership, and corporate taxes since 1987.