Is it necessary for purchase Office 365 to work with Lync 2013. My laptop works on Windows 8.1 and Office 2007 with SP3. I have downloaded and installed Lync 2013 but not able to sign-in.

Please help!

Yes, you'll either need Office365 or an on-premises Lync server deployment to sign in.

Hi,

Microsoft Lync Server is an enterprise real-time communications server. The Lync client is used to connect Lync Server. The Lync client is only meant to be used with a Lync Server (hosted in a corporate environment) or an account hosted on Office 365 with Lync functionality enabled. After you doing that you can create a user on Lync Server and login to Lync Server with Lync client.

Best Regards,
Eason Huang