Hi colin79ie
Another option would be to get the money received from your nixer (after allowing for expenses incurred in earning the money) coded into your tax credits for the year with Revenue. This can be done by contacting your local Revenue PAYE district. This way the tax due can be collected via the PAYE system and you will not be considered a "chargeable person" by Revenue.
If your net income (gross less expenses) from non-PAYE income is equal to or greater than €3,174 in a tax year, you will be considered a "chargeable person" by Revenue and would need to prepare and submit a Form 11 (as opposed to a Form 12) and pay self-employed PRSI.