It is possible that Letter 6475 doesn’t match your records, or what you actually received.
You should check your account online with the IRS’ Your Online Account portal. This will have your relevant stimulus payment information.
Letter 6475, Your Third Economic Impact Payment, was sent to EIP recipients in late January of this year. This letter also applies only to the third round of Economic Impact Payments, but would also include “plus-up” payments. According to the IRS’ IRS sending information letters to recipients of advance child tax credit payments and third Economi... page,
The third round of Economic Impact Payments, including "plus-up" payments, were advance payments of the 2021 recovery rebate credit that would be claimed on a 2021 tax return. Plus-up payments were additional payments the IRS sent to people who received a third Economic Impact Payment based on a 2019 tax return or information received from the Social Security Administration, Railroad Retirement Board or Veterans Affairs. Plus-up payments were also sent to people who were eligible for a larger amount based on their 2020 tax return.
