Required : SDK 13.0
Download link : https://developer.intuit.com/docs/0250_qb/0020_get_set_up/sdk_downloads
https://developer.intuit.com/Downloads/Restricted?filename=qbsdk130.exe

Sample Experimental Project :
https://onedrive.live.com/redir?resid=7D3B49FB4453E77A!1431&authkey=!AANhtiemRiGCDwk&ithint=file%2crar


Reference Guide: 

http://www.nullskull.com/a/1568/c-net-application-with-quickbooks-desktop-edition.aspx
https://mukarrammukhtar.wordpress.com/quickbooks-with-net/
http://qbblog.ccrsoftware.info/2010/03/quickbooks-add-on-programs-sdk/