When you upload your data it is validated against some simple criteria to check you have the right data in the right filed.  Common validation errors are listed below.  

Organisation ID We often find lots of validation errors because the wrong organisation code has been used.  the code the Grouper is expecting is shown in the upload wizard.

Dates Date formatting is often an issue.  We recommend you save your data files in xls rather csv format.  If you have to use csv make sure your dates are formatted yyyy-mm-dd.  In xls files setting the format of the date fields to a date format often corrects any issues.  Make sure you do not set other non-date fields with a date format.

PCT Codes Please make sure you use valid PCT codes, and X98 and Q99 for overseas and PCT not known respectively.

Ethnicity Please use the correct code 'Z' for Ethnicity not given.

You can review the errors in the Submission Detail page, there is a tab there called Errors, select one of the records with an error and you will be presented with a pop-up prompting you to make the appropriate correction: