The amount of tax credits
If your child is in hospital, you remain entitled to the disabled child and severely disabled child elements (see here) in your CTC, even if your child’s disability living allowance or personal independence payment has stopped. This is not likely to have happened if your child is under 18, but may have happened if s/he was 18 or over when s/he entered hospital.1Reg 8(2)-(4) CTC Regs If you are getting help with childcare costs in your WTC (the childcare element), this may change if your child is in hospital for a prolonged period. If your childcare costs stop or go down by £10 or more over a period of four weeks, you must let HMRC know about this change.
Make sure you report changes to HMRC to avoid underpayments or overpayments.