HI, From my experience it has been 12 months exactly to the day in some cases. Here is some info from Chpt 15 of our Medicare guidelines. The statues listed in here will break down this information a little more.
280.5 – Annual Wellness Visit (AWV) Providing Personalized Prevention Plan Services (PPPS)
(Rev. 170, Issued: 05-10-13, Effective: 01-01-12, Medicare Coverage of the Annual Wellness Visit (AWV);
01-01-13- Medicare Coverage of Hepatitis B Vaccine, Implementation: 06-10-13) A. General Pursuant to section 4103 of the Affordable Care Act of 2010 (the ACA), the Centers for Medicare & Medicaid Services (CMS) amended section 42 CFR 411.15(a)(1) and 42 CFR 411.15(k)(15) (list of examples of routine physical examinations excluded from coverage), effective for services furnished on or after January 1, 2011. This expanded coverage, as established at 42 CFR 410.15, is subject to certain eligibility and other limitations that allow payment for an annual wellness visit (AWV) providing personalized prevention plan services (PPPS), when performed by a health professional (as defined in this section), for an individual who is no longer within 12 months after the effective date of his/her first Medicare Part B coverage period, and has not received either an initial preventive physical examination (IPPE) or an AWV within the past 12 months. Medicare coinsurance and Part B deductibles do not apply.