Accountant maxxing means: The practice of optimizing every financial aspect of one's life to an obsessive degree - maxing retirement contributions, stacking cashback cards, tracking every dollar - often at the expense of. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.