You will forfeit equipment to CHEP and Loscam if your account balance goes below 0. It can go below 0 if you have more equipment coming off your account than going on. This can sometimes be due to timing in that the sender does not submit their transfers to the pallet hire companies in a reasonable time. It can also be that the sender has not raised transfers to your account.
Ideally you should contact the sending trading partner and get them to get their transfers processed. Many pallet controllers do not do this and ultimately the equipment is forfeited from your account. It can be some time later that the sender comes to you with a claim and by that time the pallet hire companies may not return the equipment from credit and you then suffer a loss.
If equipment goes into credit then you should do something about it. Some equipment control systems do not adequately track equipment in credit so if you use one of these systems you would have to use Microsoft Excel to record movements into and out of credit.