Why did my spouse and I get two different letters about our advance CTC payments?

Letter 6419 is a letter that the IRS sent to everyone who received monthly Child Tax Credit (CTC) payments in 2021. The letters contain information about how much the IRS issued you in these monthly payments. If you did not file a 2021 return but you received Child Tax Credit payments in 2021, in order to claim the rest of the Child Tax Credit, you will need to report the amount the IRS paid you in advance — so this letter can be very helpful. Letter 6419 was sent in December 2021 or January 2022.