The assumed yield varies by asset. For capital gains from investments it is >6% (roughly the expected return on the stock markets for the last century), for cas

The assumed yield varies by asset. For capital gains from investments it is >6% (roughly the expected return on the stock markets for the last century), for cash it is <1% (real returns used to be a bit higher but currently are extremely low, effectively overtaxing by a lot). But as already said above they are currently changing the law to use the actual yield instead, so the top level comment advice doesn't really matter anymore.