We study checkable codes in finite Frobenius and quasi-Frobenius rings and show that the Jacobson radical of a quasi-Frobenius ring is checkable if and only if the ring is Frobenius. Also, we show that in a quasi-Frobenius ring
R
R
every maximal left ideal is checkable and that
R
R
is code-checkable if and only if
R
R
is a principal right ideal ring.