Review the rules about what qualifies someone as a dependent or qualifying child because you may have listed someone who doesn't qualify. Note: This form also applies to some tax benefits, including the child tax credit, additional child tax credit, and credit for other dependents.Does anyone have sample letters to the IRS for different situations? Maybe one with code numbers and explainations. Letter 6419 includes: Number of qualifying children used to calculate advance payments, and repayment protection when filing your 2021 federal tax return. The Child Tax Credit helps families with qualifying children get a tax break. You may be able to claim the credit even if you don't normally file a tax return. The IRS issued a "lockin" letter to his employer. You can claim a child, spouse, relative, and even a friend as a tax dependent. This is how the IRS determines claiming a dependent.