[lazyasciiart]

Yes - the value of your company is the gain. It is the money you would have if you sold the whole thing.

[procaryote]

It's only a gain if you sell.

Selling a company and paying tax on the profit in tax is a completely different proposition from paying tax on hypothetical profit you haven't made (and might never make) just because you want to move.

[lazyasciiart]

That's what unrealized means. Gains you haven't got because you haven't sold.