I have overstayed my visa for 14 years. I am from Canada and stayed in the USA for the last 14 years illegally. My mom is terribly sick and I must return to Canada. I have been living with John for 13 years. He would come to Canada and marry me. He is a US citizen. We never married in the US because I had no identification. When could I come back to the US? I never paid taxes.
First and foremost, you really need a lawyer here. Looking for Internet advice in your situation is probably as "helpful" as trying to perform appendix self-surgery using Google search.
There are two reasons for this (and this is why you need one):
You said you never paid taxes so I assume you earned income in US. Assuming you also did not file a tax return, this is a separate - and more serious - crime here in USA than overstay, as one can get in jail for a year for each year tax return wasn't filed.
The issue here is complicated because of statute of limitation and other factors involved. A competent attorney might strike a deal with IRS on your behalf, so it is important to get one.
Since you were unlawfully present in the USA over a year, you may be inadmissible to the USA for 10 years (this means you cannot enter the USA for 10 years after your departure). This applies to Canadians as well according to this article. Since you came in much earlier, an immigration lawyer should be able to tell you whether those new rules apply to you or not, and - as a result - whether you are subject to ten year inadmissibility.
If you are found inadmissible, this inadmissibility can be waived IF you are married to the US citizen, but only if it causes extreme hardship to one:
(v) Waiver.-The Attorney General has sole discretion to waive clause (i) in the case of an immigrant who is the spouse or son or daughter of a United States citizen or of an alien lawfully admitted for permanent residence, if it is established to the satisfaction of the Attorney General that the refusal of admission to such immigrant alien would result in extreme hardship to the citizen or lawfully resident spouse or parent of such alien. No court shall have jurisdiction to review a decision or action by the Attorney General regarding a waiver under this clause.
Understanding what is considered "extreme hardship" and making a case to prove it is something which should be left to a legal professional.
Thus please get a lawyer ASAP.
Consider whether John could move to Canada. That might be cheaper and just about infinitely simpler. You are potentially looking at tens of thousands of dollars in legal fees to get this sorted out by a highly specialized law-firm, and there is no guarantee of success, especially if you just leave in a hurry. If you stay put and have the lawyer sort things out first, it's a lot better but still expensive and it won't be fast (think of many months, possibly years). Not to mention if there are unpaid taxes then the most you can expect from a very good lawyer is avoiding jail time and decreasing the immense penalties a bit but certainly there will be some very interesting amount of monies to pay to IRS (and potentially state/local too).
Edit: I would talk to a lawyer first, no matter which direction you want to go. Initial consultation should not be horribly expensive.
There are a few things here.
First is the potential INA 212(a)(9)(B) ban if you leave the US. Specifically, if you accrue 180 days of "unlawful presence" and then leave the US, you trigger a 3-year ban, and if you accrue 1 year of "unlawful presence" and then leave the US, you trigger a 10-year ban. But the definition of "unlawful presence" is somewhat complex. Just being out of status doesn't by itself cause "unlawful presence" to start accruing. Generally, you only automatically start accruing "unlawful presence" if you stay past the date on your I-94. If your I-94 doesn't have a date (e.g. if it says "D/S") or if you never got an I-94, then you do not automatically start accruing "unlawful presence" no matter how long you stay. The only other ways to start accruing "unlawful presence" are if you applied to USCIS for a benefit and were denied for being out of status, or if a final order was made against you by an immigration judge in immigration court in a removal proceeding; I am assuming neither of these happened.
You didn't clearly describe your status. You said you were "from Canada", but does that mean you are a Canadian citizen? (Which is kind of weird because you said "my visa", but Canadian citizens generally do not need or get US visas; perhaps you were just using the term loosely to refer to your status in the US.) Canadian citizens visiting the US often do not get an I-94, especially if entering by land (I believe they usually do get an I-94 when entering by air). Electronic I-94s only started being used in mid-2013; so 14 years ago, the only I-94 you could have gotten was a paper I-94 (a small rectangular stub often attached to your passport). Did you get an I-94? Even if you got an I-94, that doesn't mean you were admitted until a specific date on it; people on F (student) or J (exchange) status usually get admitted for "D/S", with no date. What was your status in the US? If you did not get an I-94, or you got an I-94 admitted for "D/S", you did not automatically start accruing "unlawful presence" no matter how long you stayed, and likely have not accrued any "unlawful presence" so far, which means you would not trigger a ban upon leaving the US.
Here is the information from the USCIS Adjudicator's Field Manual about people who were admitted for "D/S" (Chapter 40.9.2(b)(1)(E)(ii)):
(ii) Nonimmigrants Admitted for Duration of Status (D/S) Other Than F or J Nonimmigrants
If USCIS finds a nonimmigrant status violation while adjudicating a request for an immigration benefit, unlawful presence will begin to accrue on the day after the request is denied.
If an immigration judge makes a determination of nonimmigrant status violation in exclusion, deportation, or removal proceedings, unlawful presence begins to accrue the day after the immigration judge’s order.
It must be emphasized that the accrual of unlawful presence neither begins on the date that a status violation occurs, nor on the day on which removal proceedings are initiated.
And about Canadians who didn't get an I-94 (Chapter 40.9.2(b)(1)(E)(iv)):
(iv) Non-Controlled Nonimmigrants (for example, Canadian B-1/B-2)
Nonimmigrants, who are not issued a Form I-94, Arrival/Departure Record, are treated as nonimmigrants admitted for D/S S (as addressed in Chapter 40.9.2(b)(1)(E)(ii)) for purposes of determining unlawful presence.
If you marry your US citizen fiance, he can petition you to immigrate to the US (become a US permanent resident). You can do this either through Adjustment of Status in the US or Consular Processing abroad to get an immigrant visa. However, if you leave the US, and if you have accrued more than 1 year of "unlawful presence" (from the discussion above), you trigger a ban, which will cause you to not be able to get an immigrant visa for 10 years, unless you get a waiver, and a waiver requires showing "extreme hardship" to your spouse, which is very hard to do. On the other hand, you are eligible for Adjustment of Status in the US after marrying your US citizen fiance, and the fact that you are out of status or how long you have been out of status are completely irrelevant for Adjustment of Status in this category. And since you haven't left the US yet, you don't have a ban, so you don't need a waiver. So if you have this "unlawful presence" and you have any desire to stay in the US, and will be able to stay in the US after immigrating enough to not abandon residence, the best way by far is to marry in the US and apply for Adjustment of Status; it will be very straightforward and the fact that you've been out of status is irrelevant; no waivers or explanation needed.
However, your need to visit your mother soon conflicts with your ability to do Adjustment of Status. If you leave the US while Adjustment of Status is pending, you automatically abandon your Adjustment of Status unless you've already been granted Advance Parole before you left. You can apply for Advance Parole at the same time as Adjustment of Status, but it takes more than 4 months these days to get regular Advance Parole, and I doubt you are willing to wait that long before visiting your mother. If you have an urgent reason, you can request Advance Parole be expedited or apply for Emergency Advance Parole. I am not sure whether your mother's situation is urgent enough to qualify for Emergency Advance Parole, but it's worth a shot (quickly marry, apply for Adjustment of Status, and go in to the office to apply for Emergency Advance Parole as soon as you have the application number).
You really have no good options here. You probably know this already that it was a big mistake to go undocumented, especially for this long, and perhaps an even bigger mistake not to file tax returns.
One option is to come clean. But even if, with the help of a really good lawyer, you avoid jail time for all those years of unfiled tax returns, you'll still be on the hook for lawyer fees and for back taxes (with penalties and interest)... we are easily into the hundreds of thousands of dollars here. And you may never be able to return to the US with that record, not even after marriage.
Another option is to just risk it: Come back to Canada (there is no exit processing by US border authorities at land crossings, so they will not have a record of you exiting the country), do your thing and then try to return to the US using your Canadian passport. A bit of a nailbiter, to be sure, but you will probably get back as there is likely no record of your overstay. Unfortunately this only postpones the inevitable, as it leaves you exactly where you are right now: undocumented, with many years of unfiled tax returns.
Some suggested that you and John should just move to Canada. Makes sense except for one thing: I am assuming that you haven't filed any returns with Revenue Canada either. So guess what? They will be interested in what you earned and how much income tax you failed to pay. OK, maybe they are not as vicious as the IRS and are less likely to lock you up, but they will still come after you the moment you show up on their horizon. Once again, you'll be on the hook for quite possibly hundreds of thousands of dollars of unpaid taxes, plus penalties and interest.
At this point, the only sensible thing to do is consulting not with us random Internet fools but with a competent lawyer who is a specialist in immigration and income tax matters. In fact, you may probably need to find two lawyers, one on each side of the border, because you'll need legal help with Revenue Canada, too. But don't expect any magic solutions. This will be a long uphill battle. Good luck with it.
So, you never mention if you arrived overland or by air. This will have some bearing on whether the US knows you are here or not. If the US doesn't know you are here, or that you have been here for so long, and you were to suddenly appear in Canada, you very well might be able to get back in without any effort at all. There is, however, an issue of timing in connection with the variety of problem you have.
So, you've got a bunch of problems - one which has received very little attention in other answers - is your complete lack of identification.
Take a look at this recent news article. It you were able to somehow "magically" able cross the border and appear in Windsor, this group might be able to help you. It might be a good idea to give this group a call before your "magic" trip to start the process of getting some id. In that article, it mentions that it might take months and that you will need people to vouch for your identity. This means you'd have to find a place to stay in Canada for at least a few months.
Ultimately you might need to visit a Canadian consulate to get your ID. However, I agree with all other posts that you really need to find a US immigration lawyer to speak with to find out what your options are.
There are a lot of comments above about taxes - and the "moral" consequences of not filing taxes. I just want to note that there are tens of millions of US citizens who work in semi-legal and illegal work who do not properly file taxes. This includes most people who work primarily cash jobs - waiters and waitresses, baby sitters, nannys, cash construction workers, landscaping crews, aluminum can collectors. The lack of formal connection to the formal economy is a huge problem for these "low-wage" workers, one that will likely never be addressed.
I suggest that you begin the process of normalizing your life - get some id, get a place to live (in Canada or the US) that is known to the authorities, get a bank account, credit cards, an ATM card, and other stuff to start entering the legal working world. Eventually, you might want healthcare, to buy a house (and get a mortgage), buy a car, and to do other things connected to the formal economy. How to do this? Not sure - Canada might have social workers you can contact?
The means by which millions of people transition from the shadow economy to the formal economy in the US in other countries is not clear. However, it will require a change in mindset on your part. I have met many people who performed this transition, and in the end the agree that being in the formal economy, and connected to the social safety net, is a good thing.
So if you decide to sneak into Canada, go to your mom, I suggest you not sneak back into the US - instead, get some ID, a passport, and secure the foundations of entering the formal economy. Perhaps John has a job in the US, and can't stay with you in Canada for the whole transition period. However, if he really means it when he says he'd marry you, then having him visit you a couple times a month for 6 months won't be a big deal.