Most casino websites all have a page where you can view all your previous deposits and withdrawals, this is to keep records of your transactions Incase of any future arguments or issues, they might be able to track your deposits or withdrawal requests.
If you made a deposit into your account an it's not recorded there yet, it might be that the transaction was not successful or you need to contact their customer support to rectify the issue for the transaction board is your only proof of deposit apart from your payment slip.
If you made a deposit into your account an it's not recorded there yet, it might be that the transaction was not successful or you need to contact their customer support to rectify the issue for the transaction board is your only proof of deposit apart from your payment slip.