In order for you to collect the AWS Billing information and store it in an S3 bucket that Tim can access, you will need to create a new Cost Report. Please go to the AWS Billing Console and follow the instructions in the video below to create a new Cost Report.
Please ensure that you create a new top level bucket for your Cost Report and that you don't nest a Cost Report Folder inside another existing folder in your S3 Bucket.
Read the Docs
In order to get better predictions, if you have a longer history of reports for your account, please copy over the reports to the S3 bucket you gave Tim access to.