Many organizations have opted to provide their services on the web to remain competitive and to reach wider market space. The open nature of the Internet and lack of barriers open the door to masqueraders to spoof the identity of service provider, and deals maliciously on his behalf. Therefore, a trust mechanism has to be reliable and robust enough to protect the customer and gain his/her confidence in conducting business transactions on the web. The first step towards conducting business transaction is to acquire a certification from a third party authority. However, this certification can be subject of frauds and attacks. To enforce reliable business certification, we propose in this paper a new collaborative reputation based vetting model for digital certificate acquisition. Our model uses a collaborative reputation based on rating the subject business applying for a certification and the number of transactions conducted with the business as well as the reputation of the raters. In addition, it employs a clustering technique to determine the honesty of raters and to implement a reward-penalty approach. We have evaluated our model using a case study and the obtained results prove that our model is robust enough to ensure a reliable certification of businesses.