Reporting gain or loss on a limited partnership

[RWG1950]

Have acquired a new customer in another state (MS). We spoke by phone. Haven't yet seen his prior returns or K1's.
He tells me that he and his wife have invested over the last 25 years about $40-K (total) in about 7 limited partnerships. (not PTP'S)
These businesses are owned & operated by their son-in-law who apparently is a Super Cuts franchisee. Each K-1 pertains to each store.
Customer tells me that some of these businesses are not doing well and some have closed in recent years.
Since these are not PTP's that could be sold on the open market, my question is what is the triggering event that would allow a taxpayer to
establish and report any (net) gains or losses on the 1040 for the closed businesses?
Thanks for comments.

[kathyc2]

Gain or loss from entity liquidating assets will be line items on K1. If investor has capital remaining, that loss can be claimed in year where Final box is checked on K1.

If the entity has been having losses over the years, you will want to verify that losses were not taken on 1040 over basis.

[Snaggletooth]

Sounds like a handful, with a possibility of 25 years research. I wonder if you can get any information from the prior preparer, as the customer probably will not furnish you with 25 years of K-1s for seven limited partnerships.

If I understand it correctly (and someone please correct me if I'm wrong), the basis calculation for purposes of taking losses should be done independently for each partnership, instead of "netting" profits and losses together. Don't believe you can transfer basis elements from one partnership to another.