Some commercial services sell certificates to manuscript authors. Frequently these certificates are marketed to authors in developing countries where English is not widely spoken. These services claim that the certificate indicates that the manuscript meets a certain standard of quality. Often the certificate states that the manuscript is written in correct English. The certificate may be accompanied by editing services.
Should I pay for a certificate and send the certificate to a journal?
This is a general question is inspired by this one to avoid talking about a specific service.