How many months, at minimum, must Parmigiano-Reggiano cheese be aged before it can legally carry the name?

Answer

12 months

Every single wheel is inspected by hammer-tapping experts at 12 months, and Italian banks have accepted aging Parmigiano wheels as loan collateral — one bank held over 400,000 wheels in its vaults.

Source: Consorzio del Formaggio Parmigiano-Reggiano