Md. Code, Family Law § 10–131

(a) If the address of a recipient changes, the recipient, within 10 days after moving to the new address, shall send the change of address to:

(1) the court:

(i) by certified mail, return receipt requested; or

(ii) by filing in person at the court and obtaining proof of filing;

(2) the obligor, at the obligor’s last known address, by first–class mail; and

(3) (i) each employer who has been served with a copy of the earnings withholding order, by first–class mail; or

(ii) if the support enforcement agency receives the support payments, the support enforcement agency:

1. by certified mail, return receipt requested;

2. if the agency’s website allows parents to update address information, by entering the new address on–line;

3. by filing in person at the agency and obtaining proof of filing; or

4. by telephone or electronic communication to the agency and obtaining proof of change.

(b) If, because of the failure of a recipient to give notice under this section, an employer or the support enforcement agency is unable for a 2-month period to deliver deductions under the earnings withholding order, the employer or agency:

(1) may not make further deductions;

(2) shall return each undeliverable payment to the obligor; and

(3) shall notify the court.