There are so many factors that could cause you to see this. I'd suggest you need to do a more in-depth analysis of the data you're looking at. I think the most important thing is not to look just at the total numbers, but to look at the rate at which they are being billed. For example, has your insurance company increased the size of the population that you are covering between 2019 and 2022? If you are covering 3 times as many people, then this wouldn't represent an increase. Or is it just certain providers increasing their billing, or all providers? Is it happening in certain plans or certain localities, or all over? Is it a particular diagnosis that's being treated more often than before? 300,000 cases is too much to audit - I would start narrowing this down to see where the real problem is or might be.