Section 9. (a) If the court finds that a parent is chargeable with the support of a child, the court shall make an order in accordance with subsection (c) requiring a parent to pay weekly or at other fixed periods a sum for and toward the current support and maintenance of such child. The court may make appropriate orders of maintenance, support and education for any child who has attained age eighteen but who has not attained age twenty-one, who is domiciled in the home of a parent and is principally dependent upon said parent for maintenance. The court may make appropriate orders of maintenance, support and education for any child who has attained age twenty-one but who has not attained age twenty-three if such child is domiciled in the home of a parent, and is principally dependent upon said parent for maintenance due to the enrollment of such child in an educational program, excluding educational costs beyond an undergraduate degree. Upon the petition of a party, the court shall also order past support for the period from the birth of the child to the entry of the order, taking into consideration the parent's ability to pay under subsection (c) and any support provided by the parent during such period. An order or judgment of support pursuant to this chapter shall be entered notwithstanding the default of the defendant or his failure to appear personally upon a showing that notice was served in accordance with the applicable rules of court. For good cause shown, the court may set aside an entry of default and, if a judgment has been entered, may likewise set it aside in accordance with rule 60(b) of the Massachusetts Rules of Domestic Relations Procedure. When the court makes an order or judgment for maintenance or support of a child, said court shall determine whether the obligor under such order or judgment has health insurance or other health coverage available to him through an employer or organization or has health insurance or other health coverage available to him at reasonable cost that may be extended to cover the child for whom support is ordered. When said court has determined that the obligor has such insurance or coverage available to him, said court shall include in the support judgment or order a requirement that the obligor exercise the option of additional coverage in favor of the child or obtain coverage for the child. An order may be entered requiring a parent chargeable with support to reimburse the mother or the department of transitional assistance or the office of Medicaid or the executive office of health and human services for medical expenses attributable to the child or associated with childbirth or resulting from the pregnancy.

(b) Upon demand by either party, including the IV–D agency, the other party shall be compelled to provide a financial statement, except that the IV–D agency shall not be compelled to provide a financial statement for a recipient of public assistance, and, provided further, if no party makes such a demand, the court may require a financial statement of each party.

(c) In determining the amount of the child support obligation or in approving the agreement of the parties, the court shall apply the child support guidelines promulgated by the chief justice of the trial court. There shall be a rebuttable presumption that the amount resulting from application of the guidelines is the appropriate amount of child support to be ordered. If, after taking into consideration the best interests of the child, the court determines that a party has overcome such presumption, the court shall make specific written findings indicating the amount of the order that would result from application of the guidelines; that the guidelines amount would be unjust or inappropriate under the circumstances; the specific facts of the case which justify departure from the guidelines; and that such departure is consistent with the best interests of the child. In the event that no child support guidelines are in effect, the court shall make such order as is in the best interests of the child, taking into consideration the financial ability and earning capacity of the parents of the child.

(d) It shall not be a defense that the parent from whom support is sought has ceased to have custody or the right to custody of a minor child for whom support is sought, or that the custodial parent is interfering with the other parent's right of visitation.

(e) If the child on whose behalf an order of support is sought is a recipient of benefits pursuant to chapter 117, 118 or 119 and the department of transitional assistance, the department of children and families, the division of medical assistance or any other public assistance program has not been made a party as required by section 5, the court shall notify the IV–D agency of the order or judgment of support.

(f) In determining the amount to be paid, the court, in addition to applying the standards established by the chief justice of the trial court, shall determine whether the obligor is responsible for the maintenance or support of any other children of the obligor even if a court order for such maintenance or support does not exist. If the court determines that such responsibility does, in fact, exist and that such obligor is fulfilling such responsibility, such court shall take into consideration such responsibility in setting the amount to be paid under the current order for maintenance or support.