[putlake]

1. There are penalties for underpayment of estimated taxes. And there are even interest charges on penalties. https://www.irs.gov/payments/underpayment-of-estimated-tax-b...

2. The triple tax advantage is not ridiculous. (1) and (3) are not the same thing. 401k for example is not taxed going in (you fund it with pre-tax dollars) but is taxed when taken out. When you withdraw money from your 401k in retirement, you owe taxes on the capital gains that have accrued in the account since you first put the money in. But if you take money out of HSAs for paying medical bills, there is no tax on the capital appreciation you have enjoyed in your HSA account.

[PopAlongKid]

1. The IRS web page is not authority. See the Internal revenue code §6654. Failure by individual to pay estimated income tax (a) Addition to the tax. Like I said, it is officially (by law) called an addition to tax, not a penalty.[0] Further, it is calculated as an interest charge. There is not any further interest charged on the interest. Yes, there are actual penalties such as Failure to File/Failure to Pay that do accrue interest, but this is not either of those.

[0]https://www.law.cornell.edu/uscode/text/26/6654

2. The HSA is just a holding account. You can either pay for health expenses such as insurance pre-tax each year, or you can put it in a HSA and delay the payment. In either case, you only get one tax deduction, not two. The ridiculous claim is to say for a $1K contribution to HSA, you get a $1K tax deduction, then you get another $1k tax deduction when you take it out - not true.