Is it possible to deposit money in advance and keep it on your balance

What you are describing is Advance Pay https://aws.amazon.com/about-aws/whats-new/2021/07/aws-allows-customers-pay-their-usage-in-advance/

Details of how to register for it, and top up your balance are here https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/manage-advancepay.html

Be aware of quotas and other restrictions (such as only being able to pay in US dollars) https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/billing-limits.html#limits-ap

Knowledge centre article https://repost.aws/knowledge-center/prepay-services