Rolling budget
In one sentenceA budget that is extended continuously: whenever a month or quarter ends, another one is added at its end, so it always covers the same length of time ahead.
Simply put
A normal annual budget gets shorter as the months pass, and in October you see only three months ahead. A rolling budget always stays 12 months ahead.
It suits activities whose conditions change quickly, because you review the figures every month or quarter instead of once a year.
Example
A restaurant prepares a budget from January to December. At the end of January it removes January and adds January of the following year, and adjusts the remaining months with what it has learned, so it always has a budget for the next 12 months.
Don't confuse it with
Zero-based budgetingZero-based budgeting is a way of justifying every amount from the start, while a rolling budget is a way of continuously updating the period.