the aggregate, do not exceed 40 percent of the grant received under subsection (a). (B) Underserved populations Of the amount of subgrants provided under subparagraph (A)— (i) not less than 25 percent shall be dedicated to specialized technical assistance in serving taxpayers with disabilities, (ii) not less than 25 percent shall be dedicated to specialized technical assistance in serving limited English speaking taxpayers, and (iii) not less than 25 percent shall be dedicated to specialized technical assistance in serving Native American taxpayers. (6) Duration of subgrants A subgrant awarded under this subsection shall be for a period of 1 year and shall not be renewed other than through an application under paragraph (3). (c) Authorization of Appropriations (1) In general For each of fiscal years 2017, 2018, 2019, 2020, and 2021, there are authorized to be appropriated $5,000,000 to carry out the purposes of this section. (2) Availability Amounts appropriated pursuant to the authority of paragraph (1) shall remain available without fiscal year limitation until expended. 6. National service programs to provide tax preparation assistance (a) VISTA Section 103(a) of the Domestic Volunteer Service Act of 1973 ( 42 U.S.C. 4953(a) ) is amended— (1) in paragraph (12), by striking and at the end