An unpaid, unposted invoice will not have an option to be adjusted. If the GL distribution tab is still uneditable, ensure the invoice is not approved:
1. In Records, Invoices, open the Invoice.
2. On the Invoice tab, change the status drop-down menu from Approved to Pending.
3. Save the invoice.
4. On the GL distribution tab, make any changes needed.
5. Save and close the record.