I'm currently a stay at home mum to a 10 year old at school and will be able to claim a fair bit on tax next year because I'm still paying tax on my income and on top of that there are the extra family assistance payments at tax time which she could well be adding onto it. For 3 kids, that's a fair amount right there without anything else. If she isn't partnered she could have child support as well and be getting some of his tax return in backpay. My mum was only receiving less than half what she was meant to through the year then when my dad did his tax the year's worth of unpaid child support would be taken from his tax return and given to her. She'd put that away for all the following years' activities like school and sports things knowing she would be underpaid for the following 12 months as well.