The frequency of purging data is at your discretion. You can purge files after the bank completes the direct deposit transaction because you won't need the information again. You'll only need this file if you regenerate the interface file.
NOTE: There are instances when you're unable to update the payroll journal due to a duplicate batch. Purging will correct this issue if you set a purge date that is early enough.
The purge utility purges the transmitted direct deposit transaction files, not the generated ACH files saved on your network. You can find these files in the PR_03xxx.soa data file, xxx=company code.
Use Purge Direct Deposit Files to delete processed payroll data based on transmission dates.