Verizon Communications and Vodafone Group agreed to a $1.55 billion breakup fee if their $130 billion deal falls apart.

The company terminating the deal will have to pay the other party the fee within five days by wire transfer, Verizon said in a regulatory filing.

Verizon on Monday agreed to buy out Vodafone's 45 percent stake in Verizon Wireless for $130 billion. The boards of Verizon and Vodafone have unanimously approved the sale, expected to close in the first quarter of 2014.

Verizon shares were down 3.3 percent in premarket trading on Tuesday, while Vodafone's US-listed shares were down 1.3 percent.