Limited Partnership Lossisyributions

You can write it off as a loss in the year it becomes totally worthless. That would depend on the facts and circumstances surrounding its viability. I suggest you accumulate whatever documentation you can supporting it being worthless to support that determination before you deduct it on your tax return. The fact that the business is still legally open may or may not mean the stock is worthless.

does the last K-1 have an amount in part II, section L, ending capital account? If present, is it positive or negative?

If positive, that should represent your remaining basis for purposes of a capital loss if you conclude a write-off is proper at this time. If it's negative, that creates a tax issue because it would mean that more losses were incurred than you invested, less the cumulative net losses and distributions. This can happen when liabilities are allocated in section K-1 ending column. (also possible is that there are no liabilities allocated and ending capital is negative. This means more losses were allocted/taken than your tax basis which is not allowed. There should be suspended passive losses since your husband, being a limited partner, should not have had any active role in the operations, making any losses passive. Passive losses other than rental real estate are suspended until the partnership interest is disposed of or there is partnership income to offset them