Cristina de Borbon, sister of Spain's King Felipe VI, will stand trial on charges of tax fraud, the first Spanish royal to face prosecution in court.
Her father Juan Carlos abdicated in June after a series of scandals including an investigation into the affairs of Princess Cristina's husband, former Olympic handball player Inaki Urdangarin, who is accused of embezzling public funds.
Princess Cristina, 49, and Urdangarin are among 17 people ordered to stand trial in the case involving his Noos Foundation charity, the High Court of the Balearic Islands said on Monday.
Cristina and her husband have both denied any wrongdoing.
Urdangarin has been charged with breach of legal duty, embezzling public funds, fraud, influence-peddling and money-laundering. The princess is accused of two tax crimes.
The couple have been ordered to deposit funds with the court to cover possible liabilities - 2.6 million euros ($3.2 million) in the case of Cristina, and nearly 15 million for Urdanganrin.
They now have 20 days to deposit the money, according to a written court ruling, or face having assets seized.
King Felipe is riding high in opinion polls and has tried to modernise the monarchy, including taking rights and duties away from his two sisters, who are no longer formally part of the royal family.
Cristina remains sixth in line to the throne.