Section 12. The commissioner, upon his own motion, or upon application of an employing unit, after investigation, shall determine if an employing unit is an employer within the meaning of section eight, eight A, eight B, or eight C, and if the services performed by any individual for such employer constitute employment within the meaning of this chapter, and shall notify the employing unit of such determination.

Such employing unit may, within ten days after the mailing of notice of such determination, request that the commissioner grant a hearing for the purpose of reconsidering the facts submitted and to consider any additional information. The conduct of such evidentiary hearing shall be in accordance with the procedures prescribed by and pursuant to subsection (b) of section thirty-nine, except that the department shall be considered a party at such hearing. If the determination arises from a claim filed for benefits, the claimant shall be deemed a party to such hearing. After such hearing, the commissioner shall affirm, modify or revoke this determination and notice of the commissioner's finding shall be mailed to the parties.

An application for review of such finding may be taken to the board of review within thirty days after the mailing of the notice of such finding to the parties. After such notice to the commissioner and to the parties as said board deems necessary, it shall review the action of the commissioner, reconsider the facts submitted and consider any additional evidence presented by the parties and shall affirm such action unless it shall appear that it was made without proper cause, in which case the decision shall be modified or revoked. Nothing in this section shall prevent the commissioner after a decision by the board of review from submitting newly discovered evidence to said board, whereupon it shall order a hearing upon the subject matter after giving due notice to all interested parties.

A determination by the commissioner that the employing unit is an employer or that the services performed by any individual for such employer constitute employment within the meaning of this chapter, where no hearing has been held, a finding after a hearing, or a decision of the board of review shall be conclusive for all purposes of this chapter, and, together with the record thereof, shall be admissible in any subsequent proceedings, involving liability for contributions or eligibility for or the amount of benefits.

The commissioner or any party aggrieved by the decision of the board of review may, within thirty days after notice of such decision has been mailed by said board, bring a complaint in the municipal court of the city of Boston or in the district court in the judicial district wherein said party has its principal place of business or lives or is or was last employed and have the same remedy as provided for in section forty-two and the practices and procedure established for in said section forty-two shall govern.

If, upon a hearing in the municipal or district court, it appears that the complaint is frivolous, immaterial, or intended for delay, the court may award against the appellant double costs.

Nothing in this section shall be construed to prevent the commissioner, after notice to the affected parties, from reconsidering his determination that the employing unit was subject or was not subject to this chapter, when in his judgment it appears that because of newly discovered evidence or for any other reasonable cause the determination should be reconsidered; provided, however, that no such reconsideration shall be made after 4 years from the date of the original determination. Notice of any such redetermination shall be promptly given to the parties entitled to notice of the original determination in the manner prescribed in this chapter with respect to notice of an original determination. Any party notified of a redetermination may request a hearing within ten days after the mailing of the notice of redetermination. The conduct of such hearing shall be in accordance with the procedures prescribed by this section. Any party aggrieved by the decision on redetermination may appeal such decision. Such appeal shall be in accordance with the procedures prescribed in this section.