If you have a debit account, The Boost won’t leave you short. If you don’t have the required available funds in your transaction account, The Boost won’t come out.
The Boost is smart enough to know when your funds are low, so you don’t have to worry about switching it off yourself.
If you have an overdraft account or a line of credit, your Boost will still work when your funds are running low. It’s important to note that if The Boost takes an Overdraft or Line of Credit account into a debit balance, interest will be payable.