I have always claimed the Motor Mileage Allowance, when it comes to insurance I think if you use your car ONLY for childminding you could put insurance against your tax return. But I am sure if you can prove that your car insurance cost more because of your business you can claim the difference, so you need to get two quotes one with social, domestic and pleasure and one with business cover, if there is an increase you can prove it therefore can claim.... does that make sense, its the same with household insurance!