Why do you file a return?  If you only get SS it is not taxable unless you are married filing Joint or Separate.  Why do you get refunds?  If you have Tax withholding taken out of SS you should stop that.  

Thanks for your response. My concern is I was FILED in past 2 years, why IRS still Issue “Non Filing Verification” letter for those 2 years, can you explain this please ?

My guess is “Non Filing Verification” letter simply tells me that I do NOT Require to file in last 2 years (2017 & 2018), because my income threshold below “Filing Requirement” and IRS disregard my filing.  

More importantly, my refund comes from State NOT the federal level. 

P.S.  Does anyone have better answer for my concern

Thanks for your help 

If you filed a federal return and the ONLY thing on it was non taxable SS benefits and ALL the entries were zeros then the ZERO  return you mailed in was NOT accepted ... it was shredded/discarded since it was a non return according to IRS regs ...  thus your file shows nothing was filed.   STOP filing returns that do  not need to be filed.  

Thanks for your help, Critter. The reason I filed federal return is because I might have to file State Return. I am from NY state, base on the information I am provided, in your opinion, will I REQUIRE to file NY state tax return ?

many thanks to you  

I can't figure out how you got any refund (fed or state) with SS being your ONLY income ... you should not need to file either return.   STOP filing zero income returns.