I read about this all the time, but still feel a touch nervous. Hopefully you UA (or any airline) experts can reassure me.
I have a roundtrip ticket purchased awhile ago. I need to change the date and city of the return portion. To change the return to another date and city it would cost a small fortune thanks to the UA $200 change fee. If i leave the existing ticket as is and fly the outbound, but drop the return I can save money. I can book a one way return flight for several $100 less. So will i make it back home doing this -- only flying outbound on a roundtrip ticket, dropping the return on a Saturday and returning home from a different city on the following Monday?

You can it. It's against their T&C but they can't stop you from doing it.

If you have a FF plan with them and you have your FF number associated with the ticker AND if they figure (or suspect) that you purposefully dropped the return flight, they could cancel your FF program and you lose all your miles.

That being said if you do have your FF number associated with the ticket you're dumping, chances are good nothing will happen. Just don't make a habit of it.

Promise -- won't do it again! I can't figure out how they would make the connection. I know if you drop the outbound portion they will cancel the entire flight, but that they have an obvious record of. I would not be a happy camper to loose all my miles.

I have done it before and nothing happened. The consensus at FT seems to be that if it's your first time then you're fine.

Never done it before and have no plans to do it ever again. It's hard to imagine they would take punitive action against a frequent flier of 20+ years who regularly flies UA many times a year, but then again, who knows. Thanks for your reassurance.

re:
Never done it before and have no plans to do it ever again. It's hard to imagine they would take punitive action against a frequent flier of 20+ years who regularly flies UA many times a year, but then again, who knows. Thanks for your reassurance.

this is not the "old" UA it's the NEW UA. To be absolutely safe I'd forgo the miles and take my FF # off the flight.

You'll be fine. No need to forgo the miles.

I suggest you recheck your figures. When you amend most discount tickets, they charge you a change fee, and the excess, if any, of the cost of the new ticket over the original ticket. In other words, you get credit for the amount you already paid. If you just abandon your original ticket, you get no credit, and have to pay the full amount of the new one-way ticket. Depending on where you are going, it probably would cost you less to pay the change fee, but you won't know unless you have the actual costs to compare.

I've never known anyone who was booted out of a frequent flyer program for missing a flight. I'd be surprised if any airline has people who monitor us for such activity.

First I used UA online to get the new fare using the change my itin. I tried it several ways and unless I booked a flight with a stop, the fare was higher than just doing a one way. I then called UA because my thinking was the same as yours, Cleveland. However, the agent tried several different ways and booking the one way returned was always less, which the agent, of course said I could not do. UA wants their $200 change fee.

thanks, Seamus, for your reassurance.

While I was waiting to talk to an agent at the airport in Newark the other day, the man in front of me was wanting to make a similar change. The agent's advice was to wait until the day of departure and call and request the change, if seats were available he said the change fee would only be $75 then plus whatever other fees might apply.

I cannot verify that this is correct but you may want to call United and ask.

Yes, the same day change (SDC) fee is $75 but this is not an option because OP wants to change city. UA rules for SDC do not allow that.
From https://www.united.com/web/en-US/con...aychange.aspx:
<i>Changes are only available for the exact origin and destination airport. Connection points may be changed provided the new routing is permitted by the fare purchased.</i>