You can claim Child Tax Credit for your own children, but you can't usually claim it for the children that you foster.
However, you can claim the childcare element of Working Tax Credit for childcare charges you incur for your own children.
You should contact the Tax Credits Helpline on 0845 300 3900 to find out about tax credits.
If the local authority is making payments to you for the children that you foster, you will need to contact the Tax Credits Helpline for advice about what you can claim. You may also want to contact The Fostering Network for independent advice, www.thefostering.net.