@Anonymous_ I see at https://sa.www4.irs.gov/ola/payment_options/make_payment that I could make a payment for an amended return for 2019-2022, but those amended returns don't exist yet. So it seems to me that if I am really going to file amended returns I should just go ahead and do it and let TurboTax calculate the penalties and interest due for each year and pay everything when I submit the amended returns? If so, the question for me is "how long does it take to file an amended federal return with TurboTax?"
$2,946.60 is the total interest income. I can total up the amount of interest income for each year from this spreadsheet, which is from https://treasurydirect.gov/BC/SBCPrice and matches the NFCU receipt to the penny:
| Serial # | Series | Denom | Issue | Next | Final | Issue | Interest |
| Date | Accrual | Maturity | Price |
| NA | EE | $100 | Mar-93 | | Mar-23 | $50.00 | $114.12 |
| NA | EE | $100 | Feb-93 | | Feb-23 | $50.00 | $157.36 |
| NA | EE | $100 | Jan-93 | | Jan-23 | $50.00 | $157.36 |
| NA | EE | $100 | Dec-92 | | Dec-22 | $50.00 | $157.36 |
| NA | EE | $100 | Nov-92 | | Nov-22 | $50.00 | $157.36 |
| NA | EE | $100 | Oct-92 | | Oct-22 | $50.00 | $157.36 |
| NA | EE | $100 | Oct-92 | | Oct-22 | $50.00 | $157.36 |
| NA | EE | $100 | Sep-92 | | Sep-22 | $50.00 | $157.36 |
| NA | EE | $100 | Aug-92 | | Aug-22 | $50.00 | $157.36 |
| NA | EE | $100 | Jul-92 | | Jul-22 | $50.00 | $157.36 |
| NA | EE | $100 | Jun-92 | | Jun-22 | $50.00 | $157.36 |
| NA | EE | $100 | May-92 | | May-22 | $50.00 | $157.36 |
| NA | EE | $100 | Feb-92 | | Feb-22 | $50.00 | $157.36 |
| NA | EE | $100 | Oct-91 | | Oct-21 | $50.00 | $157.36 |
| NA | EE | $100 | Jun-91 | | Jun-21 | $50.00 | $157.36 |
| NA | EE | $100 | Feb-91 | | Feb-21 | $50.00 | $157.36 |
| NA | EE | $100 | Sep-90 | | Sep-20 | $50.00 | $157.36 |
| NA | EE | $100 | May-90 | | May-20 | $50.00 | $157.36 |
| NA | EE | $100 | Dec-89 | | Dec-19 | $50.00 | $157.36 |
| | | | | | | | $2,946.60 |
