I created an Excel spreadsheet to calculate Irish taxes which allows more flexibility over calculators that you can find online. It includes the years 2016-2018 and I’ll try to update it regularly with new rules, when applicable.
Fill in the values in the leftmost column for all sources of income and tax credits and leave everything else untouched (unless you want to simulate tax changes, of course).
I created a standalone web application, in Portuguese, for calculating the income tax in Portugal (doesn’t include Social Security contributions, pure tax calculations). It allows for employment income, business income, capital income, real estate income, pension income and different types of expenses. Unlike the Irish tax system, which I find quite simple, the Portuguese tax system is more complex and I wanted a way of estimating taxes for a given year and different types of income, and most online calculators just allow for employment income so I had to write my own.