I would definitely suggest you give them a call - it's not worth making false answers as your ex wife could use this against you in the future. (Even if the split may be amicable now, it may not be further down the road, from experience). Child tax credits goes to the main carer, so I'm not sure how they work it out - although my ex regularly has the children I still get all the Tax credit as they 'live' with me. As you want to share 50/50, she may claim and get it anyway unless you have a legal half custody of the children. Don't forget working tax credit too, your ex will probably claim this too. You are eligable if you work more than 16 hours a week and have to pay for child care. I would call them in confidence, or check the website, tell them the situation, they are very good at answering queries.. best of luck to you and your children in a difficult time..