If the minimum doc number tool is not working there are two big items to keep in mind.
1) Ensure that PSTL is installed on all instances of GP for the users who need the feature.
2) The tool only works if the document number that are the same length.
Please see the below from the PSTL documentation.
To set a Minimum PO or Receipt number:
1. To activate the new functionality that this tool offers, simply mark the second check box next to Minimum PO/Receipt # from the Professional Services Tools menu. Close the window.
2. Open Microsoft Dynamics GP menu >> Tools >> Setup >> Purchasing >> Purchase Order Processing, and then choose Additional >> Minimum PO Number.
3. Enter the minimum purchase order and receipt numbers.
4. If you do not want to use previous PO or receipt numbers, select the check box to never default to a previous PO or receipt number. The Minimum PO Number Default and Minimum Receipt Number Default fields will be disabled.
5. Choose Save.
This functionality will only work for document numbers that are the same length. If the next PO Number field is not the same length as the Minimum PO Number entered, then the system will function as it did without the customization.
