Mr. Shay Cody:

If, for example, one is a social worker and has to pay a professional registration fee in order to practice the profession - in other words, if it is a requirement - that can be written off against tax. However, unless one has a closed shop for a trade union the same does not apply; no tax is claimable in those circumstances. Ironically, given the approach of the Revenue, if it was a mandatory trade union membership situation - which is very rare - a person could legitimately claim it because it is necessary for the purposes of working in one's employment.