Actually Germany might fit because various public agencies can and do keep reserves. Going into the reserves is automatic once unemployment claims go up and insurance premiums go down (they're tied to income). When the shortfall is significant, there are calls to balance it from the general budget, but the reserves are used first.
In 2019 the unemployment ...
Many countries have sovereign wealth funds in which they put their surpluses.
Using these funds have several advantages:
Clearly separates the budget funds from the surplus.
Helps to shield the budget from variations in the income, specially if a significant part of the income is due to a single economic activity.
Limits political interference in how the ...
The german debt break, as you have already suspected, is indeed the example you are looking for, as it was created precisely for that purpose.
Let me quote from the german constitution :
"The budgets of the Federation and the Länder shall, in principle, be balanced without revenue from credits. The Federation and Länder may introduce rules intended to ...
I'm pretty sure that nearly all countries have that hidden sack for a bad day.
Russian equivalent of it is Stabilization Fund with a very simple rule:
when the price for Urals oil exceeds the set cut-off price, money goes to that fund.
when the price for Urals oil hits lower than cut-off price, money may be used to fill budget deficit.
That cut-off price ...