Tax Credit and UC Migration

HI I was just wondering when you move from tax credit to UC do we inform HMRC of this move? How would this create an overpayment and can this be challenge?

Hi,
When a claim to UC is made DWP will inform HMRC and the tax credit claim will end.
HMRC will send the customer a TC603 (In year finalisation notice) replaying the customers circumstances.
The customer will need to check this and tell us if any of the information is correct.
The customer may be asked to provide income details.
HMRC will finalise the claim and notify the customer if they have been overpaid.
If there is an overpayment the debt will transfer to DWP for collection.
Thank you.