Should I pay for a certificate showing the quality of my manuscript before I submit it to a journal? 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.
No (reputable) journal is going to give any weight to such a certificate when assessing a paper. If the editor/reviewers aren't satisfied with the quality of the English, they will reject the paper.

Thus, paying for a certificate for its own sake is a waste of money. Of course, if the certificate is issued in conjunction with editing services, there may (or may not!) be value in the overall package.