Argentina is making it harder for people to buy U.S. dollars to pay for travel abroad.

A new rule published Monday says anyone wanting to buy dollars for travel must first prove their money was obtained legally, and provide the tax agency with trip details including why, when and where they are traveling.

Many Argentines only declare part of their wealth and income to evade taxes, and use black-market currency exchanges to convert their inflationary pesos into dollars. Travel agencies are the latest target since they manage multiple currencies and offer customers black-market rates for their money.

President Cristina Fernandez is cracking down to keep hard currency from flowing out of Argentina, which needs the dollars to maintain its central bank reserves and pay debts.