The Rashba on Rosh hashana(15a) says when the chachamim said not to blow the shofar on shabbas there is no problem of bal tigra.The Turi Even concludes from this that if one does not perform a positive commandment he is oiver on bal tigra.
Q:In Yoma(86b) it says if one does not perform a positive mitzvah tshuva is enough but a lo taseh you need yom kippur as well.This that the Turi Even says that one who deosnt perform a positive mitzvah is oivar on bal tigra(la taseh) then one should need yom kippur as well for being oiver a positive mitzvah?
A:Rav Shlomo Zalman: By a lo taseh one performs an action,but by not doing an action(positive mitzvah)one is just missing an action which tshuvah suffices for.(M’rafsin Igri)