This is Social Security's summary of new rules it recently published in the Federal Register:
The final rules at 20 CFR 404.1574(c), 404.1575(d), 416.974(c), and 416.975(d) remove the additional conditions that we used when we evaluated a work attempt in employment or self-employment that lasted between 3 and 6 months and use the current 3-month standard for all work attempts that are 6 months or less. Under these rules, ordinarily, work you have done will not show that you are able to do substantial gainful activity if, after you worked for a period of 6 months or less, your impairment forced you to stop working or to reduce the amount of work you do so that your earnings from such work fall below the substantial gainful activity earnings level. The new rules at 20 CFR 404.1592c and 416.999a allow a previously entitled individual to request EXR [Expedited Reinstatement] in the same month they stop performing SGA [Substantial Gainful Activity].
The new rules are effective on November 16, 2016, except for the Expedited Reinstatement changes which are effective on April 17, 2017.