Israel had (maybe still has?) what was called “angel taxing” which said investment in a startup (for some definition of startup) is optionally marked to zero at

Israel had (maybe still has?) what was called “angel taxing” which said investment in a startup (for some definition of startup) is optionally marked to zero at the point of investment, which means that if you had any gains, you could net them against this investment. This is the opposite of deferring capital gain taxes - it is pulling capital losses forward. If the startup folds, the marking down is justified. If it is successful, the capital gains when eventually selling it reflect the zero base; so overall, taxes stay the same except it incentivizes capital investments immediately after capital gains.