<prompt> Human: Last year, my parents AGI was 36k, we owed the IRS about 60. Fast forward this year, my parents AGI is 41k, after inputting the number, we were informed that we owed 1700. Thats over 30 of the 5000 additional income that my parents made. I know thats not how tax work, and that the number is what the number is. But this just feel so unfair. Then again, Im just ranting because I feel really stuck.On a side note, the real number we owe is around 3100, I just simplified it down for the sake of demonstration. The other 1400 is what we owe in Advanced Premium Tax Credit, which we never knew was even a thing, or that we need to report income change every month or else we would get slapped with a huge bill at the end of the year. We live in Mass., so I cant even report the change online through the healthcare.gov website. The only direction Ive obtained so far is If you live in Massachusetts, you will use the Massachusetts Health Connector website to find assistance. But guess what, there isnt even a page on the state website with direction how to report income change. So now my parents is stuck with a bill equivalent to a month worth of both their paychecks combined, guess well live on ramen and tap water.  <response>: Its possible that when you look at the tax form you will see that the increase in income tax from 36K to 41K is a smaller number appropriate to their tax bracket, and its Earned Income Tax Credit on line 66 that is going down. They are on the phase-out down ramp of EIC, so you might see that drop by 800 or 1000 depending on number of children.No sympathy from me about your not reporting income change to Mass Health Connector. The web site address is printed on the letter they receive every month that shows their premium and payments. Tax credit merited goes down as income goes up.we never knew was even a thing, or that we need to report income change every month or else we would get slapped with a huge bill at the end of the year.This is clearly stated when your parents accepted advance premium tax credit, and is reiterated many times in the mailings from Mass Health Connector that your parents received. Using Form 8962 will show how much they pay back. There is a cap on how much they repay but I think you can expect them to repay several hundreds. It will depend on household size. This acts like a 9 marginal tax if they are in 300-400 federal poverty range; more like 13 if they are in 200-300 FPL range. But really it could be thought of as an increase in the cost of their portion of health insurance premiums.Fundamentally, your rant is a complaint that refundable tax credits intended for low income taxpayers are tapering off as they earn more income. 