How do I file for legal representation for my uncle who passed away in December? He didn't have a will or any assets.

Looks like he had no estate. You being beneficiary to his insurance does not get probated. That money is yours. Same with the bank acct if your name was on it sand beneficiary. The only thing that may be in question is his SS check. They haven't taken it back so he must have been entitled to it. I don't see why you would have to set up being a representative when he has passed. I would call the SS office. Otherwise, you have nothing to probate in my opinion.

Im sorry for the loss of your uncle. It sounds like you took very good care of him. 
This is an interesting question. I think both FF and Joann make good points.
Your friend used the term “ legal rep” but I think that could also be “ executor”.

For what month was the check issued? We assume it was the last check received but maybe not.

If for December then the moment you cashed (deposited) it you might have had a problem. If you haven’t heard from SS perhaps it is because the check hasn’t been cashed. On the other hand I would assume your friend told you that the last check was not to be cashed (depending on date of death). Too bad it wasn’t automatically deposited in his bank account from the start where it would have already been taken back if not valid. Of course after all this time it’s too late to go that route.

So thinking this out logically...,who does the check (if valid) belong to?......the estate of the deceased.
There was no will filed to settle the estate because apparently this check is the only property in the estate as all other property was outside a will.
The next question I asked myself is who would or could be the legal representative? That would be an executor, yourself most likely, if appointed. You can’t appoint yourself.
Who could appoint that person? A lawyer can’t appoint you. A lawyer could advise you. But I think it leads you back to being the executor (legal representative) of the estate. Which means the County Judge has to appoint an executor to handle the estate. (State laws being different as FF said-you would have to check. )
So depending on how much the check is for, and after checking directly with SS,
I would then go to the office in your area that probates wills (or call them) and ask what are the fees for a small estate with no will and see if it makes economical sense to go forward on your own or with an attorney.      These filing fees are often posted online on the website. 
Then you will know if you need an attorney.
A phone call could probably get you the attorney fees plus filing fees etc. You could make that call right now.
At any rate, I hope you come back and let us know what you find out.
We learn from each other.
There always seems to be a lot of confusion on these two issues. The last SS check and to probate or not to probate an estate because of the perceived expense of probate.

I would ask SS office how to go about getting it done. Maybe it is their form you have to fill out and submit along with death certificate. I'm just guessing here but I would start there before spending money on a lawyer.

Thanks for the update.
I have an aunt I take care of who never had children. While she has a will, all her assets have been taken care of outside the will for when the time comes. So my thinking has been that I would not have to probate her will.
However, She is a widow whose husband was involved in one of the original asbestosis lawsuits which has been pending for well over 30 years. Should she pass before this lawsuit settles I will have a similar problem with that check should it ever come in. So I was interested in researching this a bit. What I decided was any assett of a deceased person constitutes an estate. Estates without wills can still be probated. There are provisions for small estates. ( less than $50,000) but at some point the estate is too small to justify the cost and aggravation of becoming the legal representative or executor of the estate.
Now that’s what I discovered for my state. In your state there may be a different provision for very small estates.
I guess the moral of this story is to cash a gov check ASAP.

Moe - your uncle would be considered to have died “intestate” as he died without a will. How to get through will be whatever legal system is set by your states laws for intestate. SSA probably has info as to what is acceptable documentation for intestate for SSA specifically. This is what 97 & Polarbear are getting at. Perhaps take your valid state ID, uncles death certificate, along with something that show his address and your address as the same, and his last 6 bank statements for wherever his SS was direct deposited into and go to a SSA office to clearly find out what exactly will suffice. 

What seems to often be the system for intestate is for all assets to escheat to the state (state in control of ownership) till a “lineal heirship” determination is done & approved by PC. If that’s your states system, lineal -to me - are not ever a DIY as there’s notifications that have to be published over time (maybe 3-6 months). Dying intestate is one reason why so many states treasury & tax assessors have $&property that are considered unclaimed funds as there’s no defined owner to transfer the asset to via probate court like there would be for someone who dies with a will that names an executor and who gets what as defined by the will.

My state - Louisiana - had huge coffers with lots of $ & property left from the displacement due to Katrina. Lots of unclaimed insurance checks. For $ it went to State Treasures’ office and our new treasure -Schroeder- actually decided to make it consumer friendly with a FAQ how to get unclaimed funds. His office did a series of weekend “come & get it” at malls all over the state with huge lists of the UC in papers published like 2 times weeks before plus on line and he ran TV & radio spots. The one at Lakeside Mall had lines out the door. Lots of happy folks (& future voters) that weekend. I mention unclaimed funds cause if Uncles Estate is teeny, it’s can be more $ to get an atty than what it’s worth. Sometimes folks just wait it out till a UC can be filed with State Treasurers Office. Look to see what your states website has for UC.

? for you....the bank account that got his SS monthly check, when he died did he live the entire month before his death? Like alive all of November.If so, then the check SSA paid in December (his month of death) would be the last income check from SSA. Was a check paid in Dec? And that what your seeking? Or is it a January check? If SS pays the month after, that will be clawed back. There is no more income payments from SSA unless there are dependents like a surviving spouse or dependent children, which each get an increase to the SS checks they are already receiving. SSA will pay a one time $255 death benefit to them.

If Uncle had $ left in his bank accounts, then it’s up to banking laws as to how that $ can be accessed. If he did it POD to you, then it’s yours. Otherwise it goes into probate court or unclaimed funds system.

So Moe
You already knew what was required to be his legal representstive? What state are you in? 
Was it something your uncle would have had to of signed?
So you are saying SS took the check back in error? Then when you wrote them they agreed it was owed him but you had to come up with legal rep in order to actually have it made out to you instead of uncle? 

To be a leagal representative you have to file a petition with the court, and anyone dealing with a family member who is I'll let older should do this ASAP. While they are alive ...it makes it much easier to deal with all of the leagal issues.

Thank you Moe for coming back and giving us more information. The probate was the only thing I could find online that might work.
An affidavit of heirship I am familiar with to support title of real property so maybe it will work. Come back and let us know.

97yearold,

I will I'm going to try the affidavit it's worth a try.

I'm in Wisconsin, he would've had to sign papers making me his legal representative meaning I would've had to take care of all his financial situation, become his payee for SS his medical, and all the other stuff, but he was in his sound mind until a couple days before he passed. SS didn't take the check back in error he got his check deposit every 2nd Wednesday of the month unfortunately he passed away before his deposit date, but what sucks is he was alive for the month of November which is what the check was for December, but once he died before deposit SS is notified by the funeral home, so I called the SS and ask what happens to his check that gets deposited, they said they will take it back and send a letter to his address where he gets notified by the SS, which is my home address to the family of my uncle, they said fill it the form and send it back, so I did, they all your relationship to the deceased, I say I'm his niece, they write back and say it can only be paid if to spouse, children, parents or legal representative, which I am neither, so I spoke with a friend who works at the social security office and they said to try and get appointed his legal representative of the estate, but I spoke to an attorney today and his said that won't happen now that he's passed away, that I would have to go to probate and it really wouldn't be worth it since it was only one check that has a value of about a $1000. He suggested that I try online and download affidavit Wisconsin transfer by affidavit, he said not sure if it would work but it's worth a try, I could hire him but by the time all was said and done there wouldn't be anything hardly left, so I'm going to try the affidavit thing and see, if not I'll ask SS how long it will take for them to put it, if even happens in to Wisconsin unclaimed property... I'm in the process now of trying to claim unclaimed property for my great uncle who was my grandmothers brother whom I was his leagal representative, but it was way too complicated to try and get, I didn't have all of his a paper work that I needed and now I just have to provide lineage my mom's and grandmothers death certificate. So wish me luck, thank you all for your in put.