Scammers are sending physical letters to cryptocurrency holders that copy the look of official IRS notices.

The letters tell recipients they must enroll in something called a Digital Asset Compliance Portal before a deadline, or risk penalties.

“If you receive a letter claiming to be from the IRS that instructs you to enroll in a Digital Asset Compliance Portal, don’t respond. The IRS did not send it. The IRS does not operate a Digital Asset Compliance Portal. This is a scam,” IRS wrote.

Coinbase, working with threat intelligence firm DarkTower, published its own breakdown of the scheme after a customer reported receiving one of the letters.

DarkTower traced the site’s infrastructure to a domain registered through a…