I'm also thinking that 50/50 is reasonable and equitable. I would dock future time, even if it carried over to next year to spread it out, rather than get money back. Please get an agreement in writing.
Hopefully, they are apologetic. But, if they don't seem reasonable and equitable in whatever process you have, I think you need to write them up, consider probation, consider discharge, and consider an audit for embezzlement.
I wonder if an agreement like this is legal, should it come to a labor board dispute. You might ask your medical society to ask the labor board for a ruling anonymously if any of these employees give you the sense that they might not want to be reasonable about it.
Since it seems that the employees knowingly took advantage of you, you cannot trust these employees to protect your practice. What a heartbreaker if they knowingly took advantage. Why wouldn't a biller tell you the paycheck system was broken? I know it's business, but you want respect in both directions.
Very weird group dynamics if two employees thought they could get away with it and didn't tell the others, while the others didn't try to get away with it, but also didn't want to tell you the paycheck system was broken. You may not be able to trust the second timid group much more than the first group. Maybe the second group want the first group to get fired and didn't stop it earlier. Who told the office manager?
Office manager has some responsibility, so might want to overreact, and you need a new payroll service.
