This goes far beyond this board to help.
One comment is, the statute of limitations for the IRS to assess back taxes is 3 years, or 6 years if you understated your tax by more than 25%. There is no statute of limitations if the IRS alleges deliberate fraud. So either they are making some serious allegations against you, or they have been sending you letters for at least 4 years (to collect 10 year old taxes on a 6 year statute of limitations.). The clock on the statute of limitations only starts to run when you file, so if you never filed for those years, the statute of limitations will never run out.
The IRS won't send your case to collections until after they have tried several times to work with you. Is this the first you ever heard from the IRS? Maybe you moved and they didn't have your address, or maybe you have been ignoring years of letters. This could also be a scam. You can check your IRS account online yourself, you want an account transcript and your tax return transcripts. Make sure this is an IRS debt and not a scam.
https://www.irs.gov/individuals/get-transcript
Or, this might be a state tax return issue. For example, another taxpayer asked for help when the state of California assessed several years worth of income taxes because the state said the taxpayer lived in CA but never filed. In fact, what had happened was the taxpayer was legal guardian of his father and used his father's CA address on some paperwork, so CA got the idea that the son was also a CA resident even though he was not. Is there some state that thinks you are a resident and owe tax returns that you never filed?
You need to think this through, figure out exactly who is billing you and what they allege, and then find an attorney for the amounts you are talking about. If it is a legit IRS debt, they may accept a lower amount as an "offer in compromise", especially if you can pay it as a lump sum all at once.
