The IRS plans to start sending out the new advance child tax credit payments to eligible taxpayers on July 15th.  Letters are being sent to taxpayers who appear to be eligible for the advance credit payments.

https://www.irs.gov/newsroom/irs-sending-letters-to-more-than-36-million-families-who-may-qualify-for-monthly-child-tax-credits-payments-start-july-15