Hedge-fund manager John Paulson owes about $1 billion in federal and state taxes this year, The Wall Street Journal reported Wednesday, citing people familiar with the matter.

That figure is on top of about $500 million he paid late last year, the report said, citing sources. Paulson declined to be interviewed by The Wall Street Journal, and a representative did not immediately respond to a CNBC request for comment.

Paulson rose to prominence by betting against subprime mortgages ahead of the financial crisis. The trade earned him and his funds billions, the bulk of which he deferred tax payments on. The bill for that trade is now due, the report said, citing sources.

The firm has not fared well in recent years. Assets under management have plunged from a peak of $38 billion to less than $9 billion, mostly belonging to Paulson himself, the Journal said, citing sources.

The hedge fund has been selling parts of its stake in Caesars Entertainment so it can have enough cash to allow Paulson to withdraw his money, the report said, citing sources.

Read the full Wall Street Journal report here.