Electronic Journal of Differential Equations, Vol. 2020 (2020), No. 04, pp. 1-19. Title: Convergence of approximate solutions to nonlinear Caputo nabla fractional difference equations with boundary conditions Authors: Xiang Liu (Sun Yat-Sen Univ., Guangzhou, China) Baoguo Jia (Sun Yat-Sen Univ., Guangzhou, China) Scott Gensler (Univ. of Nebraska, Kearney, NE, USA) Lynn Erbe (Univ. of Nebraska, Lincoln, NE, USA) Allan Peterson (Univ. of Nebraska, Lincoln, NE, USA) Abstract: This article studies a boundary value problem for a nonlinear Caputo nabla fractional difference equation. We obtain quadratic convergence results for this equation using the generalized quasi-linearization method. Further, we obtain the convergence of the sequences is potentially improved by the Gauss-Seidel method. A numerical example illustrates our main results. Submitted January 11, 2019. Published January 10, 2020. Math Subject Classifications: 39A12, 39A70. Key Words: Caputo nabla fractional difference equation; upper and lower solution; generalized quasi-linearization method; Gauss-Seidel method.