This article was updated on June 19, 2017.

Changes in late 2015 to Social Security have stirred up a lot of debate, with critics bemoaning the loss of the file-and-suspend strategy and the ability to file as a spouse first. Yet regardless of how you feel about the changes, one confusing aspect about the loss of these Social Security strategies is exactly when they disappeared -- and who is grandfathered in and still be able to use them going forward.

Grandfathering: an unexpected break

In the past, Social Security changes have often come with little warning at all and have taken effect immediately. That has left those who didn't take advantage of key strategies out of luck. For instance, back in 2011, the Social Security Administration eliminated the ability for those who had claimed Social Security benefits more than 12 months in the past to withdraw their previous application. This strategy had allowed people to get a "do-over" by paying back past benefits -- interest-free -- and then potentially refiling at a later date to get higher monthly payments going forward. The SSA didn't grandfather anyone or give a grace period, drawing criticism from those who had planned to take advantage of the provision at a later date.

Image: Social Security Administration.

With the latest Social Security changes, though, there are grandfathering provisions. They're different for each strategy, and they don't cover everyone. But they do cover a fairly broad set of circumstances that gave those who do qualify a considerable amount of flexibility in moving forward with their Social Security strategy.

File-and-suspend and the six month rule

For the file and suspend strategy, the new law set a 180-day time limit from the date of passage of the law during which anyone who qualifies can start using the strategy. Anyone who has already filed and suspended or who does so within that time frame will be able to benefit from the strategy on an ongoing basis into the future. That 180-day period ended on April 30, 2016, effectively closing the door for those who want to initiate the strategy after that date.

To use the file-and-suspend strategy, you need to have reached full retirement age. If you didn't reach your 66th birthday before the time limit expired at the end of April 2016, then you weren't grandfathered in. Technically speaking, you'll still be allowed to suspend your benefits after that date if you want, but if you do, then no one in your family will be able to receive family benefits based on your work record while your benefits are suspended.

Social Security card and money.

Image source: Getty Images.

For those who were 66 or older by the end of April 2016, the key was to make sure you got your benefits suspended in time. Because the end of the grandfathering period fell on a weekend, most advisors told clients to get their applications in by Friday, April 29, 2016. Only suspensions done before the deadline avoided the negative consequences of the law change. If you suspended, however, then you opened the door for family members to benefit well into the future.

Filing as a spouse first and the 62nd birthday rule

The filing-as-a-spouse-first strategy is also disappearing, but its grandfathering provisions involve a much longer time period. Under current law, if you haven't reached full retirement age, then when you file a claim for spousal benefits, you're automatically deemed to have claimed your own retirement benefits as well. If you have reached full retirement age, however, you can make a restricted application to receive only your spousal benefits. That lets your own retirement benefit grow.

The new law extended the automatic deeming provision up to age 70, wiping out the benefit of a restricted application. It came with a fairly generous grandfathering provision that applies to anyone who reached age 62 by Jan. 1, 2016. Anyone who met the age requirement on that date can file a restricted application at any time in the future, without anything similar to the 180-day provision of the file-and-suspend grandfathering clause applying.

The interesting thing about this grandfathering provision is that it covers something that might not happen for years. If you turned 62 in late 2015, then you won't be able to take advantage of filing as a spouse first until late 2019, when you reach the full retirement age of 66. That gives those in their early 60s a lot of flexibility that the file-and-suspend grandfathering rules didn't.

Think fast

The grandfathering rules covering Social Security's recent changes deserve close attention. For those considering filing as a spouse first, they don't require immediate action. Yet with the file-and-suspend deadline at the end of April 2016, if you haven't already taken action, then the sun has set on your being able to use that strategy before it disappeared.