If the only thing you ever do is deposit cheques, how can the balance go negative?
1. Deposit check 2. Funds are made available to you 3. You withdraw the funds 4. The check is later marked as fraudulent and the payer bank attempts to claw back the funds, with your account balance at zero
[1] https://repeater-builder.com/molotora/gontor/25120-bw.pdf