What is the best month to file to get the most DRC, delayed retirement credits, until the SSA updates their system to give full credits? Is it December or January? If I file three months ahead, according to the SSA, to get a January payment, I would need to file in October. Also, according to the SSA, the January payment is not payable until the following month. YOu must have lived the entire month to collect.
There isn't necessarily a 'best' month, but in order to immediately receive credit for all of the delayed retirement credits (DRC) you've earned up to your month of benefit entitlement you would need to choose as your month of entitlement either a) the month you reach age 70, or b) January of one of the years between the month you reach full retirement age (FRA) and age 70.
You do not have to file in advance of your month of entitlement. For example, if you reached FRA in June 2018 and wanted to choose January 2019 as your month of entitlement you could file your application anytime from September 2018 through July 2019. And yes, you're right that Social Security normally pays benefits for the month of January in February.
Before filing, you should strongly consider using our maximization software to compare your options and determine your best filing strategy.