Can I return or refuse Certified Mail?

Unfortunately, due to USPS regulations, we are required to accept and receive mail for our active customers as presented in USPS DMM 508:

A CMRA may not refuse delivery of mail if the mail is for an addressee who is a customer or former customer (within the past 6 months). The agreement between the addressee and the CMRA obligates the CMRA to receive all mail, except restricted delivery, for the addressee.

Some people have asked about whether refusing mail will show that they have never received it.  In regards to proof of mailing, whether it be accepted or refused or returned, it does not really make a difference since the sender has proof that they did mail it.  In general, that's usually sufficient to establish that the sender has made effort to notify the recipient.  For example, when evicting a tenant, the landlord is required to mail written notice to the tenant.  Tenant can choose to refuse or return or accept.  It does not matter since if the issue ever goes to court, the landlord shows that he attempted to notify the tenant as required by law.  

Although it's our understanding this is how it works, your situation may be unique or different.  It's advisable that you contact your lawyer regarding this issue. 

But ultimately, it makes no difference in how things are processed.  We are still required to accept certified mail for active customers as required by USPS regulations.