Del. Code tit. 19 § 3359
If any employing unit neglects or refuses to make any assessment report required by the rules and regulations of the Department for a period of 30 days after the date on which the assessment report should have been made or if any assessment report which has been made by an employing unit is deemed by the Department to be incorrect, the Department may make an estimate and determination of the liability of such employing unit from any information which the Department may have or may obtain and, according to such estimate and determination so made, may assess the employing unit for the assessments, interest and penalties due from the employing unit and may give notice of such assessment and determination by registered mail or other delivery method authorized by the Department and may make demand upon the employing unit for payment. Such assessment and determination shall, based upon administrative determination of the Department, be final and conclusive as to such employing unit's liability and the amount thereof, only until such time as the employing unit submits the required assessment report(s) to the Department, or unless the employing unit shall protest such assessment and determination within 15 days after the mailing or delivery of the notice by other delivery method authorized by the Department. If any employing unit protests the assessment and determination, the employing unit, upon its written request, shall be heard by the Department. Such hearing shall be conducted according to the procedure prescribed by the Department. Immediately after the hearing the Department shall notify the employing unit of its findings and the assessment and determination then made, if any, shall be final and conclusive as to the liability of the employing unit upon the issuance of such notice.
19 Del. C. § 3359