Prepare a small representative import
Review the source file before uploading it. Remove unnecessary information, identify duplicates and agree which existing records should be updated rather than recreated. Map dates, identifiers, categories and account relationships explicitly. Test a sample containing ordinary records and difficult cases, such as missing values or unusual characters. Reconcile the imported result with the source so you know what was accepted, changed or rejected.
Treat an export as a new information copy
A downloaded file may no longer be protected by the application's access controls. Limit exports to the people and fields required for the task, and decide where the file will be kept and when it will be removed. Use exports for a defined purpose, such as finance reconciliation or a migration review, rather than creating repeated uncontrolled copies. For recurring data exchange, a properly scoped integration may be more maintainable than manual spreadsheets.