One must separate maintenance income from capital income (assessments), else the IRS will treat all as maintenance.

But, if there is a clear delineation of capital income (assessments, e.g.: accrued over ten months and kept in a separate account), then the shareholder upon the sale of a unit, can take the original price of the coop and add to that number the sum of all capital assessments as well as any self initiated capital improvements to generate an updated cost basis for tax purposes, e.g.: sale price (less expenses) – cost basis = tax burden (if any).