It is Medicare fraud for a physician (or anyone else, for that matter) to bill for work they did not do.
If the attending reviews charts at the end of the day, and the bill goes out with the resident's billing number, that's perfectly kosher. Some insurance carriers will pay for resident care. Some will not.
If the attending puts their own name on the bill, that's fraud. It's fraud even if there is no charge attached to the visit (i.e. the 90 day globals). Kinda funny that you can be fined for submitting bills with no charges on them.
The Primary Care exception codes are much more complicated, and clearly don't apply to the situation described above. In a nutshell, if a physician is supervising no more than 4 residents, and doing nothing else at the same time, then visits of level 1 - 3 do not need face-to-face time by the attending physician -- review of the case during or immediately after the visit is sufficient. In any case, it won't apply at all to the case above.
I would note that, should you report this, you MIGHT be able to collect on a very hefty whistleblower fee. Usually the fines for this sort of thing run into the millions, as technically you can be fined $10K for EACH event (although it's never really that much). A whistleblower gets 10-15% if I remember correctly.
You remember correctly and this is 100% on the mark. There have been several hospitals that made the news for medicare fraud. One the hospital ( big university) admitted responsibility, got a discount and paid up. The nearby community hospital didn't and paid dearly.
Never, ever blow the whistle from a position of weakness. As a resident you are weak and the institution is powerful. If you think it is a real problem, then keep very good notes, never on your person, and never at work. Keep them in a safe place. Lab notebooks with numbered pages are a good record, prosecutors love them as they are hard to alter without detection. Then document what you see, keep your mouth shut and wait until you are no longer under the thumb of the institution, and they can do you no harm. Be squeaky clean yourself and do not participate in Medicare fraud, yourself as they will hang you out to dry, if they can.
Once you complete the program, talk to a competent attorney. The law you need is the Federal False Claims Act, which dates back to the reconstruction era when the feds were being sold bad meat. You and your attorney can decide if you have a good case, and if so, draft a complaint and file what is known as a Qui Tam action on behalf of the government. The complaint is sealed and turned over to the U.S. Attorney who then has the option of pursuing the claim or not. If he decides to pursue the government takes over from there and you turn over your stuff wait and if the government collects you get your cut.
If the US Atty declines to run with it, and you and your attorney think you have a case and big enough return, then you can run with it and collect a far larger percentage if you recover government money.
If you do this while a resident you're likely to need to find a new profession. If you do this after residency as an attending, you are likely to be much more (but not completely) immune. Remember, there is a tremendous good ole boy network, you'll be outside of the miscreant's network, but they too have enemies, and as long as you can steer clear of your now former institution by all means have at 'em, as long as you are sure you can prove your story.
At one institution, interns and PGY2 were doing chest taps and belly taps solo and later the attendings came by and signed "present and actively participated in..." and billed Medicare. This one got dinged $54M, the feds offered to settle for $24M and the hospital declined. The final bill was $63M. It ain't chump change, and 10% of $63M will buy a couple of extra bottles of wine, but do this while you're working there, and it'll be a long and thirsty wait. And if you lose, you are toast and you'll never work in the field again.