As stated you are taxed as per the payment made in one month so do not have the benefit of getting three months tax credits. If you expect to be back in work fairly soon, then the new place will adjust your pay accordingly. If you need to get a rebate you need to fill in a form and send it to your revenue office. I believe it used to a be a P50 form but it may have changed. Check out revenue.ie. Make sure to sign on immediately, don't wait till the 12 weeks are up.