Hi @Avyayah
When you export a report to a CSV file, it ignores formatting and layout, as well as the following items during rendering: headers, footers, custom report items, automatic subtotals, and so on. For more details, you can refer to this link: https://learn.microsoft.com/en-us/sql/reporting-services/report-builder/exporting-to-a-csv-file-report-builder-and-ssrs?view=sql-server-ver16.
You can choose a suitable output format or change the report design to better suit the CSV format.
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Best regards,
Aniya