The CFO of Vonage Holdings Corp.(VG) is leaving the company some time this year, but didn’t say why.

John Rego has worked for Vonage, an over-the-top VoIP provider, since 2002.

In a Securities and Exchange Commission filing, Vonage said Rego has agreed to stay in his positions – which also include treasurer and executive vice president – until Vonage files its annual report for 2009, and until his replacement is chosen.

Vonage told the SEC it will detail the terms and conditions of Rego’s departure at a later, undetermined date.