“Now they are demanding that I pay all the taxes that I owe (somehow they took my word on my earnings, but not on my tax payments) along with interest. What do I need to do in order to remedy this?”----> When you , as a taxpayer, receive your W-2s in the mail, it should include three copies. One copy is for the local government, one for state and one for federal. W-2s are always required. You have to file an amended return, showing ALL your income including what you already filed plus the additional amount. I guess If you are a MD resident and e-file your MD tax return, you are not required to send a paper copy of your W-2. You are required to submit the information printed on your W-2 electronically as part of the e-filing process. Your W2 includes the ER's name, address and the ER's MD Employer Identification Number in box 19 of the W-2, as well as state disability insurance withholding in box 14(if MD imposes the tax), the state wages in box 16, state income tax withholding in box 17, and any local taxes withheld and the taxing locality in boxes 19 and 20. If any of the required information is missing, the e-filed state return will be rejected. The Dept of Rev compares this electronic information with information reported by the ER on his state ER tax forms. Since you forgot to attach the required state copy of your W-2 to your paper-filed MD resident tax return, you need to, wait for the DOR of MD to contact you and request the form. You need to send the W-2 with a copy of the notice you receive. Do not send the W-2 alone, an amended return or another copy of the original return with the W-2 attached. Failing to attach the form when you originally file will delay the processing of your tax return, but there is no penalty for this error. There may be additional penalties and interest on any unpaid taxes, and it will also delay any refund due to you. So I guess you need to keep contacting DOR of MD for more info in detail.