In most cases if you go abroad, you can only receive WTC for up to eight weeks. This can be extended up to 12 weeks if your absence is in connection with the treatment of an illness or disability.
Your daughter will need to provide evidence to HMRC of the treatment she is receiving in France and evidence that this is why she is there. If she spends longer than 12 weeks in France, then she will no longer be able to claim WTC.
She must declare to HMRC that she is abroad and let them know of any changes to her income to prevent her being overpaid or underpaid WTC.
David Samson is a welfare specialist at Turn2us