So this was a verboten subject in the round table because it's political but I was surprised to hear that in her testimony and I think it deserves discussion.
On it's face it seems like a spectacularly bad idea that could destroy the entire capital markets. For example if they simply "marked to market" at the year end stock closing price then applied tax just as if the assets were sold it would be devastating for anything that was not yet long term which would mean going forward there would be no reason to want to invest. At the same time for long-term holders the massive selling that would be required across all holders having unrealized gains would greatly depress the stock price such that much more than 15% of holding would need to be sold because the idea that any amount of stock can be sold for the same price that the last single share traded at is pure fiction. Prices would collapse and those with the greatest unrealized capital gains might even by bankrupted because the forced selling could depress prices so much that even selling 100% of the position might not yield 15% of the ore-collapse market value. It would be the end of the stock market as we know it.
Because that direct approach is so certain to lead to catastrophe I'm confident it won't be proposed. But there are other possibilities. For example they could tax all unrealized capital gains (less any unrealized capital losses) at a low rate, say 1% and then reset the cost-basis to be equal to the "marked to market" price used to calculate the tax. That could bring in a one-time large windfall of tax revenue which may be the goal while actually providing a massive gift to the wealthy. I'm not sure this is a good idea either but it's an idea that might not be a non-starter.
I think there are more sensible ideas that could allow the wealthy to pay their fair share of taxes. One loop-hole that needs to be fixed is the way that the ultra-wealthy avoid taxes altogether by having no income and instead borrowing money against stocks (with massive unrealized capital gains) pledged as collateral. They get a fabulous low interest rate and have no income nor capital gains yet can effectively have a very large amount of money at their disposal. This problem could be solved by treating the act of pledging stocks as collateral for a loan (probably excluding margin loans used strictly for investment) as a "marked to market" sale (and resetting of the cost basis) of the stock for tax purposes. So you'd be hit with capital gains taxes if you monetize your stock but it's up to you if you want to do that. I think that would basically mean people would just have to sell stock if they want the money rather than borrow against it It seems a lot fairer and more reasonable than taxing unrealized capital gains.
Eliminating the stepped-up basis for inherited stocks is another thing to consider to prevent the ultra-wealthy from escaping taxes. This could be done on a sliding scale similar to how the inheritance tax is done so that small estates might have a full stepped-up basis, larger ones could have some less-than 100% step and very large estates could have nearly no stepped-up basis.
On it's face it seems like a spectacularly bad idea that could destroy the entire capital markets. For example if they simply "marked to market" at the year end stock closing price then applied tax just as if the assets were sold it would be devastating for anything that was not yet long term which would mean going forward there would be no reason to want to invest. At the same time for long-term holders the massive selling that would be required across all holders having unrealized gains would greatly depress the stock price such that much more than 15% of holding would need to be sold because the idea that any amount of stock can be sold for the same price that the last single share traded at is pure fiction. Prices would collapse and those with the greatest unrealized capital gains might even by bankrupted because the forced selling could depress prices so much that even selling 100% of the position might not yield 15% of the ore-collapse market value. It would be the end of the stock market as we know it.
Because that direct approach is so certain to lead to catastrophe I'm confident it won't be proposed. But there are other possibilities. For example they could tax all unrealized capital gains (less any unrealized capital losses) at a low rate, say 1% and then reset the cost-basis to be equal to the "marked to market" price used to calculate the tax. That could bring in a one-time large windfall of tax revenue which may be the goal while actually providing a massive gift to the wealthy. I'm not sure this is a good idea either but it's an idea that might not be a non-starter.
I think there are more sensible ideas that could allow the wealthy to pay their fair share of taxes. One loop-hole that needs to be fixed is the way that the ultra-wealthy avoid taxes altogether by having no income and instead borrowing money against stocks (with massive unrealized capital gains) pledged as collateral. They get a fabulous low interest rate and have no income nor capital gains yet can effectively have a very large amount of money at their disposal. This problem could be solved by treating the act of pledging stocks as collateral for a loan (probably excluding margin loans used strictly for investment) as a "marked to market" sale (and resetting of the cost basis) of the stock for tax purposes. So you'd be hit with capital gains taxes if you monetize your stock but it's up to you if you want to do that. I think that would basically mean people would just have to sell stock if they want the money rather than borrow against it It seems a lot fairer and more reasonable than taxing unrealized capital gains.
Eliminating the stepped-up basis for inherited stocks is another thing to consider to prevent the ultra-wealthy from escaping taxes. This could be done on a sliding scale similar to how the inheritance tax is done so that small estates might have a full stepped-up basis, larger ones could have some less-than 100% step and very large estates could have nearly no stepped-up basis.