The title compound, [Na(C(2)BF(2)O(4))(CH(3)CN)(2)](n), forms infinite two-dimensional layers running parallel to (010). The layers lie across crystallographic mirror planes at y = 1/4 and 3/4. The Na, B and two F atoms reside on these mirror planes. The Na(+) cations are six-coordinate. Two equatorial coordination positions are occupied by acetonitrile mol-ecules. The other two equatorial coordination sites are occupied by the chelating O atoms from the difluoro-(oxalato)borate anion (DFOB(-)). The axial coordination sites are occupied by two F atoms from two different DFOB(-) anions.