When sending sensitive data, it's often wise to ensure the file isn't accessed by anybody else, or that it remains online for longer than necessary.
The best way to achieve this, is with "one time download links". These links will automatically expire after the file has been downloaded once.
The file will no longer be accessible, and will be moved to your "trash", where it will be permanently deleted after 7 days, or immediately if you clear your trash.
To create a one time download link, upload your file, then from your dashboard, hover over the file action button, and click "one time download", then simply enable the switch in the modal.
Once enabled, click "save & close" and share the file URL. As soon as it's downloaded, it will expire.