Hi Kate
no formula here.......i assume you and the husband are jointly assessed to tax so should you not use your credits he wiil get them automatically so is the case in your standard cut-off
you dont mention how much your reduced salary is but ill guess it will be 3/5 of €45K being €27K
Gross Take Home Pay €27,000.00
Tax €2,280.00
Take Home Pay after Tax €24,720.00
Less PRSI €1,355.84
Net take home pay €23,364.16
you have used all your credits but have unused standard rate cut-off of €5K which your husband can use and save him tax of €5K at 22% being €1,100 per year