Section 80B. The holder of a title acquired under section seventy-nine or eighty, whether acquired before or after the effective date of this section, may file in the land court a petition to establish such title by requiring all persons who would have an interest in the land involved except for either the petitioner's title or his chain of title originating under section seventy-nine or eighty to show cause why they should not bring an action to try any claim or claims which they may have adverse to the petitioner's title arising out of the tax proceedings upon which such title was based. The petition shall set forth on oath the petitioner's source of title, giving a reference to the place, book and page of record of the deed under section seventy-nine or eighty upon which the petitioner relies, the description of the land involved which appeared in the tax deed or instrument of taking upon which such deed under section seventy-nine or eighty was based, the names of all such persons known to the petitioner and such other facts as may be necessary for the information of the court; but the petitioner need not allege in such petition nor show during the hearing thereof any error or irregularity in the tax proceedings upon which such title depends or any other defect in such title. The petition shall be in the alternative praying that such persons be ordered to show cause why they should not bring action to try such claim or claims or, if such persons do not appear within the time fixed or, having appeared, disobey the lawful order of the court to try their claim or claims, that the court enter a decree that they be forever barred from having or enforcing any such claim or claims adversely to the petitioner, his heirs or assigns, in the land described.

If any such persons are unascertained, not in being, unknown or out of the commonwealth, or cannot be actually given notice and made personally amenable to the decree of the court, they may be made respondents and, if they are unascertained, not in being or unknown, may be described generally, as the heirs or legal representatives of AB, or such persons as shall become heirs, devisees or appointees of CD, a living person, or persons claiming under AB.

Upon the filing of the petition, the court shall notify all such persons of the pendency of the petition, the notice to be sent to each by registered mail and the return of receipt to be required, the addresses of such persons, so far as may be ascertained, being furnished by the petitioner. Such other and further notice by publication or otherwise shall be given as the court may at any time order. The notice, to be addressed ''To all whom it may concern'', shall contain the name of the petitioner, the names of all respondents named in the petition, the description of the land, and a statement of the nature of the petition, shall fix the time within which appearance may be entered and shall contain a statement that unless the persons notified shall appear within the time fixed that they shall be forever barred from having or enforcing any such claim or claims adversely to the petitioner, his heirs or assigns, in the land described.

If, after notice has been given and the time limited in such notice for the appearance of the respondents has expired, the court finds that there are or may be respondents not actually given notice who have not appeared, or who are minors, or persons under disability, or unascertained, unknown or out of the commonwealth, it may of its own motion, or on the representation of any party, appoint a disinterested person to act as guardian ad litem for any such respondents. The compensation of the guardian ad litem shall be determined by the court and paid by the petitioner.

After all the respondents have been given notice as hereinbefore provided and after the appointment of a guardian ad litem, if such appointment has been made, the court may proceed as though all respondents had been actually notified. Such petition shall be a proceeding in rem against the land, and any decree entered as hereinafter provided shall operate directly on the land and have the force of a release made by or on behalf of all respondents of all claims adverse to the petitioner's title.

The persons so notified shall by answer show why they should not be required to bring an action to try such claim or claims, and the court shall enter an appropriate decree relative to bringing and prosecuting such action. If the persons so notified do not appear within the time fixed or, having appeared, disobey the lawful order of the court to try their claim or claims, the court shall enter a decree that they be forever barred from having or enforcing any such claim or claims adversely to the petitioner, his heirs or assigns, in the land described; provided, that such decree shall not be entered unless the petitioner has proved to the court that the collector's deed or the instrument of taking, as the case may be, upon which the petitioner's title depends, was duly recorded within the time provided therefor by law. No petition to vacate such decree and no proceeding at law or in equity for reversing or modifying such a decree shall be commenced by any person except within one year after the final entry of the decree if the decree is entered on or after September first, nineteen hundred and forty-six, or within one year after said date if the decree was entered prior to said date.

If, as the result of a petition filed under this section, the petitioner's title is adjudged invalid by a court of competent jurisdiction because of errors or irregularities in the tax proceedings upon which it was based, the clerk, upon request, shall issue a certificate to that effect. The treasurer of the city or town where the land affected by such title is situated, upon receipt of a release by the holder of said title of all interest which he may have under it, together with such certificate, shall refund to such holder the amount paid therefor but not exceeding the amount received by the city or town.