yes, if your husband is resident in Ireland he must register with the tax office as a self assessed individual which means he will have to submit an income tax return in Ire in Oct every year (that he has this foreign income). He will get a credit for the German tax paid against any Irish tax liabilty so depending on what his Irish & German tax amounts to he may not actually have an Irish tax bill (even though if hes only paying 13% German tax its likley he will have an Irish liability) but not having an Irish tax liability does not discharge him from being obliged to actually having to register as self assessed and submit a return. I would advise ringing your local tax office.