Hi Manal-Hafza,
Thank you for your response. When a deposit is paid for a purchase, the deposit amount is typically posted to an asset account for the purchase (which can be set from Setup >> linked account). When the purchase order is converted to a bill, the software needs to transfer the deposit amount from the applicable account and post it to your trade creditors account (this is PJ1171-21510). This is known as a "transfer of deposits". However, in your case, you manually entered the payment, and that's why it's creating the negative balance. There's no option to delete the transfer deposit, so you'll need to delete the manual payment entry (CD 1481).
For further information about this, kindly refer to this Help article: Supplier Deposits.
Please let me know if you require any further assistance with this. I'm happy to assist.
Cheers,
Princess