An invoice has an entered date for three months ago but is approved today. The financial period in the invoice should be this month, but Maximo uses the financial period of the entered date.
This is working as designed. The Invoice Financial Period was derived from the Invoice's Entered Date. Maximo has always used the Entered Date on the invoice to derive the financial period as that is when the invoice was created and the client wants it to fall in that financial period regardless of when it is paid.
However, Maximo does allow the entered date to be edited if the user wants to change it. Users can change the invoice status to Waiting for Approval (WAPPR), and then change the entered date. In this case, if the financial period belonging to the date three months ago is closed, Maximo will ask the user if they want to use the next open period.
In version 7.5, Maximo has added an enhancement which provides the user with a new field called G/L Posting Date that is used to determine the Financial Period. This helps users to keep the entered date and the financial period date separate.