From the voyage drawer actions it is possible to change the Voyage Reference Number or Voyage Number, depending on the voyage status.
When voyage status is Estimate, Unallocated or Allocated, it is possible to change the Voyage Reference Number.
When voyage status is Nominated, Operational, Operationally Closed, Invoiced or Closed, it is possible to change the Voyage Number.
Clicking Edit Voyage Reference... or Edit Voyage Number... in the options meny opens a dialog box where the current values can be modified. In addition, the dialog box contains a field for changing the Voyage Start Year.