I filed and suspended in April 2016. I reach 70 on December 11,
2018. I've been told by SSA I need do nothing to begin receiving benefits at
age 70. Assuming this is true, when should I expect to receive my first
benefit check? Also, is there a way to ensure that SSA will indeed recognize
that I want to end the suspension at age 70? Or should I contact SSA and tell
them to end suspension on November 30, 2018, so I get benefit in January,
2019, since SSA will pay for December 2018 only if I date my end of
suspension on or before December 1?
Assuming that Social Security processes your reinstatement timely, you should get your first payment on the 3rd Wednesday of January 2019. That's when Social Security will pay benefits due for December 2018 for most people whose birthdays fall on the 11th through 20th day of a month.
Reinstatements at age 70 are automatic if you don't request reinstatement sooner, so it doesn't sound like any further action of your part is required. You may want to check with Social Security to make sure they have your current bank account number on file for direct deposit, though.