When importing data into Jira, the most important thing is to prepare your input data file and make sure it is formatted correctly and contains all the necessary information. To help the importer, keep the following in mind:

• Remove any non-data-related content, especially if you created your CSV file from a spreadsheet, which will help to keep the file size down.
• If your file contains users who need to be imported into fields such as Assignee, make sure you use either their usernames or email addresses that can be matched against corresponding accounts in Jira.
• If your file contains dates that need to be imported into fields, such as Due date, make sure they are all formatted using the same date format. This is so that Jira can process date values consistently.