If you or the IRS changes your federal return, you must file an amended Virginia return within one year of the final IRS determination. Generally, for a credit or refund, you must file Form 1040X within.You can now file Form 1040X electronically with tax filing software to amend your Form 1040, 1040SR, or 1040NR for the current or two prior tax periods. You can find the CP or LTR number on the right corner of the letter. Your income tax return is due April 15, 2024. Your income tax return is due April 15, 2024. Notice of Tax Return Change letters contain one or more alphanumerical code at the bottom of the page. An example is provided below. Skip to Main Content. Javascript must be enabled to use this site.