BP,

You mentioned,"- Flip tax reduces capital gains they'll pay on their sale profit. (I know bldgs that push this idea and I'm not sure if/how it works, so check it with your coop accountants!)"

Are you sure? I know that in a single family home, for example, one can add capital improvements to the basis of the house. Thereby, the sales profit is reduced and taxes are reduced. But, how can one do this from a flip tax which is supposedly used for capital improvements that have yet to come.

Also, how can a shareholder add his share of the capital improvements to his basis?

In all previous discussions on flip tax, passing it to the buyer is best. If you want to live in this building, contribute to the coffer. And then, it is the offer of the seller to pay it for the buyer, just like closing costs.