Withholding Locked

I’ll try to make this brief. A few years back, well between 2017 and 2023 I owed back taxes. I’m currently on an $850 a month payment plan with the IRS which is a huge chunk of my income per month. I’ve been working with the taxpayer advocacy service the IRS offers but it really hasn’t helped a ton. Recently I found out the key culprit to me having to owe each year was a lock in letter that was locking in my taxes at a married lower rate. I’m not married and haven’t been since 2020ish.

The TAS had me write a letter explaining the lock in letter and they’re trying to lift it. However, is there anything that can be done with my huge payment plan amount? I’d love to free up some of that and make it less difficult to make ends meet.

I feel like the lock in letter at the lower rate really messed me up and with all the penalties and interest I’m never digging out of this hole.