If my mother forget to pay our property taxes, would Chicago Board of Equalization have sent us the bill?

Is there a tax exempt program for those over 65 usually if the home has been owned and lived in for a number of years? There is here, it is over 65 and have lived in the home more than ten years.

Check the county treasurer website where you can look up payment information.

I’m assuming the property has been owned outright for ages, so paying property tax bill is totally responsibility of the owner. Is this accurate?

Where exactly is the property?
You mention Chicago Board of Equalization, but you’re in California, so is it actually the California Board of Equalization? and if so just how old are the letters your elder / you have from CA BOE?
OR
is this a property actually in Chicago/ Cook County?

Whatever the case, if the bill is actually from years ago, and taxes have not been paid for years, it has gone up for annual tax sale that the county in which it is located is required to do annually on delinquent properties. If it’s been over 3-6 sequential years (the timeframe required is very interdependent on your states property / real estate laws), there has been the ability for those holding prior years tax sale deeds (they paid delinquent tax bill) to legally acquire the property by filing a tax sale deed redemption on the property at the courthouse.

To find out what has happened, as a first, start by finding the 14 digit PIN on an old tax bill and go on-line or call the county tax assessor/ collector to see what the current status is on the property as to ownership. The # is what GardenArtist references in her post. Also, Freebrowers suggestion on using Redfin is an awesome idea!

fwiw I’ve done a bunch of tax sales and a couple of actual redemptions, by & large I’ve found in my area most who do tax sales DO NOT do them to actually acquire the property. They do tax sales to get the very hefty interest that is placed on delinquency plus the initial tax bill $ that all gets paid to them when the old owner finally finally pays the delinquent taxes due usually when the house gets sold. Interest is anywhere from 18% to 30%, it’s serious passive income to be made. But if this is a home in CA, well y’all’s real estate market is crazy high so I bet folks do actually do redemptions to be able to flip. Even if it’s an old run down home, it’s valuable for CA real estate market. So my suggestion is find out if it’s been sold via tax sale redemption and if it has you imo will have to have a real estate attorney do either a “sale in error” declaration or “redemption under protest” type of filing to try to reacquire the house. Good luck.

FHA and VA loans usually have you pay taxes and home insurance in with your Mortgage payments. This is call escrow. Because of the times property taxes are due (my every quarter) the bank may be a little late paying the taxes. Mom should be getting a bill. That bill should be carrying over any outstanding amounts and the new amount. If they don't, Mom should be getting paperwork showing that taxes were not paid and how much the late fees would be.

I live in small town and I can go up to the tax office and get info on my account. I stopped paying Moms taxes when she died and got a letter when a lien was put on her house.

Mimsy, I can't speak to all jurisdictions on when they report taxes as unpaid, i.e., the next year, or some other time at which delinquency occurs.  E.G., my community provides residents less time than my father's community to pay taxes, so delinquency would occur earlier.   I don't know how they get away with this, but don't have the time to check it out.  

So, this would make a difference when an unpaid tax is reported as delinquent.  This is critical as a tax sale could occur if the taxes are unpaid for the statutory period established.  

Do you know how to read title work?    Encumbrances, easements, unpaid taxes, liens, mortgages, deeds and other legal documents are reflected in title work, but it also depends on what you ask for  in title work. 

E.g., when law firms for which I worked needed to file foreclosure proceedings, we requested a foreclosure search, which is very thorough and identifies any entities that might have claims for unpaid liens, and whose interests would need to be "extinguished" (legal term) before clear title could be conveyed, free of liens, to the mortgagee (lender).

Title work for a sale would reflect which interests have filed secured liens against the property and would need to be discharged before a clean title sale could take place.   There are more issues, including beneficial encumbrances (easements) vs. liens and secured interests.

So, what kind of a search did you order?   BTW, Chicago Title was at the time I was working a top notch title company, and one we used for large commercial transactions.

What you can do is refocus from the last sentence in your opening description to determining the status of the unpaid taxes BEFORE a tax sale takes place.    Call Chicago Title and ask for a copy of the unpaid tax bill.    You can also ask the local taxing authority about the status of the taxes, and perhaps you might get a copy of an unpaid bill from them.

Doublecheck that the bill applies to your mother's property, by using the Sidwell, a number used to identify properties by other than a street address.

I.e., a Sidwell could be 2 numbers, dash and a series of other numbers. 
They're also called "parcel code numbers."   An example would be something like 55-22-34-367-789.  It is possible someone at a local level made an error, so focus first on confirming that the unpaid taxes are in fact for your mother's property. 

Sidwells are shown on tax bills, as well as recorded documents (or at least they used to be when I was working).   They're also shown on Assessment Notices.  

If you have any questions, please feel free to ask.   I worked in commercial real estate transactions for the big law firms for several years and would be glad to offer additional insights if appropriate.

Mortgage Companies and banks will often secure the taxes being paid automatically in your mortgage payment. They pay the taxes.

Unless the mortgage was paid off, or refinanced by another bank, the bank should have paid the tax.

Anyone (the public) can access the County Tax Assessor's office in person, by phone, or online.

You did a title check with Chicago Title (paid for it?), ask them for the information. But inform yourself by accessing the County Tax Assessor.

Was the unpaid tax recent? The title company showed "a tax" unpaid.
Are you aware of the year, or years it was unpaid? Surely that cannot be for a period of ten years. You might want to get help gathering your information on your mother's (your Aunt's) finances.

If it’s in San Diego County, try https://www.sdttc.com/content/ttc/en.html
as if you are trying to pay this year’s bill. It will list the owner and payment date.

If you don’t have the APN handy, you can probably find it on the property’s Redfin listing under public facts.

You could have an outstanding tax bill.

Just curious, has this been going on prior to 2013 or is it the last 10 years? Because I find it hard to believe that the property hasn't been seized in a tax sale.

What address does the county assessor show for the bill? They send them out annually, so how did this get missed for 10 years would be what I would find out.

I think the members of the Forum would be about the last ones to know what's up with Mom's property taxes or bills.
You will need expert advice to find out how to trace down what is owed in taxes I think. You can try to trace this all out with Chicago Title or at least use them for a place to begin your research. I am assuming you are POA and can access this information. Then go to your county records to see if there are taxes owing or liens of any kind.
This isn't something you can afford to be wrong about so I would myself seek advice of Elder Law Attorney just on how to check out everything.