New E/M coding criteria for 2021

We do not have professional billers at our organization.  It is required that our providers have an understanding of the codes they are selecting to bill.  With the new changes to the E/M coding we are wondering if we are selecting the E/M level based on Medical Decision Making can we bill both the E/M plus an add on psychotherapy code if the prescriber is providing psychotherapy during the session.  Client is scheduled for 30min appointment the prescriber selects a 99214 based on MDD and provides 20 minutes of psychotherapy can they bill both 99214 and 90833?  Can we bill a 99213 +90833 for a client who is seen for 40 min when selecting the E/M based on MDM? We appreciate any information that may be provided.