Automated security systems provider ADT  (ADT) - Get Report set off alarm bells with investors Tuesday after reporting a fourth-quarter loss that missed analysts' forecasts.

Shares of ADT were down 12.6% to $6.64 on the New York Stock Exchange. The stock ended the day Monday at $7.59, up 21 cents.

ADT late Monday reported a fourth-quarter net loss of $149 million, or 20 cents a share, vs. net income of $638 million, or 99 cents a share, in the comparable year-earlier period. On an adjusted basis, the company reported a per-share loss of 4 cents, well below the profit estimate of 12 cents a share of analysts surveyed by FactSet.

The net loss was due to the prior year's income tax benefit of $725 million related to U.S. tax reform, and a goodwill impairment loss of $88 million in 2018 due to underperformance of the company's Canadian business.

On the sales front, revenue for the quarter was $1.185 billion, up 7% from a year earlier and above analysts' expectations of of $1.16 billion, driven by monitoring and "related services" revenue, which includes signing on new recurring customers, and installation and other revenue, which includes commercial installations and monitoring.

For the full year, ADT reported a net loss of $609 million, or 81 cents a share, compared to net income of $343 million, or 53 cents a share.

For 2019, ADT said it now expects revenue of $4.9 billion to $5.1 billion vs. consensus forecasts of $4.92 billion.