I work 30 hours a week with a 20 minute lunch break every day. Is my employer allowed to deduct this lunch break and claim I now only work 28.20 hours per week?
If you are clocking out for lunch and not working during lunch, then those hours can be deducted from your total hours for the purposes of determining Full-Time status.
However, if you are working through lunch, then those hours would be counted.
The rule is that employers can only deduct time an employee wouldn't be working. To deduct lunch the employee must actually take the break and not work.
This matters for health insurance, as larger employers are mandated to provide health coverage to full-time employees, and thus the Full-time status question comes up regarding health insurance and the ACA.