Charter Stock Is Tumbling 14%. Why Earnings Failed to Wow Investors.

Charter Communications operates the Spectrum pay TV and internet services. (Courtesy Charter Communications)

Charter Communications stock was plummeting on Friday after the telecommunications company missed Wall Street’s earnings forecast.

Shares tumbled 14% to $325 in early trading. Rival Comcast was also falling, down 4% to $33.95. The S&P 500 was up 0.2%.

The selloff came after Charter, which operates the Spectrum pay TV and internet services, reported second-quarter adjusted earnings of $9.18 a share, as revenue climbed 0.6% from a year ago to $13.77 billion. Analysts were expecting earnings of $9.58 a share on revenue of $13.77 billion, according to a FactSet poll.

Charter added 500,000 mobile lines over the quarter, which was roughly in line with Wall Street’s expectations. It lost about 417,000 subscribers across its internet, video, and wireline voice services.

Charter said in May that it had agreed to acquire fellow cable TV provider Cox Communications in a deal that valued Cox at $34.5 billion.

If regulators approve the deal, it would create a vast new company with a presence across the country. Charter has about 31 million customers, and Cox has around 6.5 million.

Write to George Glover at george.glover@dowjones.com