Millions of retirees, disability recipients, and survivor beneficiaries woke up this week checking bank accounts for what the Social Security Administration considers the final regular payment wave of May. The latest deposit cycle applies specifically to beneficiaries born between the 21st and 31st of any month, a group some financial commentators have started calling “Group C” under the SSA’s staggered payment system. Here’s what you need to know about why these checks arrive later in the month.