Field help (GSTGRPSTA) 

Select a status to keep track of your workflow. This is recommended and not required.

In review = This indicates that you have not yet finalized data for this group and period.

Validated = This indicates that you have confirmed the data, but the period is not yet closed. You can still make modifications and reset to In review if desired.

Closed = When you select this option, you can no longer make modifications to the data and Update GST data is no longer active. This closes the period and you can no longer change the status.