(CNN) Former San Antonio Mayor Julián Castro said he plans to release 10 years of his tax returns as part of his 2020 Democratic presidential bid.

"I'm going to release 10 years of tax returns with plenty of time for people who are going to go caucus in Iowa and then of course everybody who's going to vote after to digest them," he told CNN's Brianna Keilar in an interview on "Right Now" Friday.

Castro did not specify when he would release his tax returns. His campaign told CNN that he does not plan on releasing his taxes until they've been filed this year. The tax season ends on April 15.

Castro called on President Donald Trump, who's claimed he's under audit by the IRS, to release his tax returns.

"He clearly doesn't want us to see something there and hopefully Congress will be able to get a hold of them," Castro said.

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