Spanish authorities, who estimate that Spaniards are holding on to more than €1.6 billion worth of soon-to-be-worthless pesetas, would like everyone to dig out their stash and trade it in for Euros.
Economists would like to see the money in circulation, helping the economy, although there's a good chance that some of the missing money is just that—lost on the ground, accidentally discarded, under sofa cushions and more—and that an additional chunk is in the form of bills and coins that have collector value greater than their monetary value.
Spain has been on the Euro since 2002, replacing the peseta. Originally, December 31, 2020 was set as the last day for exchanging them, but this week, the government extended the deadline to September 2021. Exchanges can be made at the headquarters of the Bank of Spain in Madrid, or by mail.
One wrinkle: Notes produced during the 1939-1975 Franco dictatorship and after are eligible for exchange, but those produced during the 1936-39 civil war must first be analyzed by experts to confirm if they are authentic.