In general, the tasks a biller or coder is permitted to perform is an internal employer decision. There are some employers that do not even permit certified coders to change without clinician approval. That being said, particularly for a smaller employer, where employees may sometimes perform work a bit outside their title, it might be permitted, depending on the circumstance or employee. Medical coders are not licensed, like an RN where there are specific activities they are legally allowed to perform or not perform. Legally, anyone may code, but ultimately the clinician is responsible.
I personally did coding work for an independent practice for several years before I was certified. But I was skilled, had 10+ years of experience in medical billing, and did thorough research to understand gyn surgical procedures which is what I was coding for.
Summary of MY OPINION:
In a large employer, I cannot imagine this being permitted.
In a smaller employer, it would depend on the skill of the person and the specific circumstance. Like - was the code selected N83.9 which is Noninflammatory disorder of ovary, fallopian tube and broad ligament, unspecified, but the clinician writes "Adult osteomalacia" which is M83.9. In that scenario, it seems more like the biller is correcting a typo rather than selecting a diagnosis. No coder or biller (certified or uncertified) should be assigning
diagnosis codes that are not documented by the clinician.