At step 4 of Social Security’s sequential evaluation, the SSA considers whether or not you have the ability to return to your past relevant work. The SSA considers your past work, both 1) as you performed it (and described it in your Work History Report), and 2) how that work is generally performed in the national economy. See Ruling 82-61.
To determine how the work is generally performed in the national economy, the SSA looks to the Dictionary of Occupational Titles (DOT) for a description of your job. For example, if you were a cashier, the SSA would look at the requirements of that job both as you described it and as it is described in the Dictionary of Occupational Titles.
I just had this discussion with a client. His claim was denied at Reconsideration because, according to Social Security, he was able to perform one of his past relevant jobs as generally performed in the national economy. The client was adamant that he could not perform that job, given all the walking it required. He even sent me a read-out from his Apple watch showing how many steps a day he took while performing that job (7,500 steps a day on average, if you are wondering). But it doesn’t matter, because Social Security will also consider how that job is generally performed in the national economy.
You have to be prepared to rule out the claimant’s ability to perform past relevant work both as performed and as generally performed in the national economy.