Up to $10k/year, and they're currently paying 9.62%. There's no other way to get a guaranteed return anywhere near that, and everyone should buy as much as they can afford to. You're basically saying no to free money if you don't.

> Tax free too.

I bonds are not tax free.

They can be tax-deferred, and some (educational) uses of interest gained can be tax excluded, for some people.

There is a cap of how many you can purchase in a given tax year, though. 8k or something IIRC.

$10k per person though you can supposedly double that with trusts somehow.