Mainstay Funds Trust N-14 Registration statement for investment companies business combination

Exhibit 14(b)

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form N-14 of our report dated May 27, 2022, relating to the financial statements and financial highlights of the Fiera Capital Small/Mid-Cap Growth Fund, a series of Fiera Capital Series Trust, appearing in the Annual Report on Form N-CSR of Fiera Capital Series Trust for the year ended March 31, 2022, and to the references to us in “Additional information about the Funds” under the heading “Financial Highlights”, “Appendix A - Article IV - Representations and Warranties”, and “Appendix D - Financial Highlights of the Funds” in the combined proxy statement/prospectus, which are part of such Registration Statement.

/s/ Deloitte & Touche LLP

Milwaukee, Wisconsin

March 10, 2023