  Flag kernels are tempered distributions which generalize these of
Calderon-Zygmund type. For any homogeneous group $\mathbb{G}$ the class of
operators which acts on $L^{2}(\mathbb{G})$ by convolution with a flag kernel
is closed under composition. In the case of the Heisenberg group we prove the
inverse-closed property for this algebra. It means that if an operator from
this algebra is invertible on $L^{2}(\mathbb{G})$, then its inversion remains
in the class.
