You can apply from when your child is 18 months, but if you apply too early it will show as 'not found' or 'unsuccessful'.
The best time to apply is when your child turns 2 years old, or the week when your child has their 2nd birthday.
If you receive a letter from BMBC (Barnsley Council) you still need to apply. The letter alone is not proof of eligibility, and will not be accepted by childcare settings. The letter tells you how to apply.