WASHINGTON (BLOOMBERG) - For President Donald Trump, Tax Day isn't today - it'll be Oct 15.

Trump filed an extension for his 2017 tax return "as do many Americans with complex returns", White House Press Secretary Sarah Huckabee Sanders said in a brief statement.

"He will file his tax return by the extension deadline of Oct 15, 2018," she said.

The President has contravened a tradition followed by US presidents and major presidential candidates going back decades by refusing to release any of his tax returns, saying his lawyers have advised him not to because he's being audited.

No law prevents Trump from releasing his tax returns, regardless of whether they're subject to an IRS audit.