77 Pa. Stat. § 731
On or after the seventh day after any injury shall have occurred, the employer or insurer and employe or his dependents may agree upon the compensation payable to the employe or his dependents under this act; but any agreement made prior to the seventh day after the injury shall have occurred, or permitting a commutation of payments contrary to the provisions of this act, or varying the amount to be paid or the period during which compensation shall be payable as provided in this act, shall be wholly null and void. It shall be unlawful for any employer to accept a receipt showing the payment of compensation when in fact no such payment has been made.
Where payment of compensation is commenced without an agreement, the employer or insurer shall simultaneously give notice of compensation payable to the employe or his dependent, on a form prescribed by the department, identifying such payments as compensation under this act and shall forthwith furnish a copy or copies to the department as required by rules and regulations. It shall be the duty of the department to examine the notice to determine whether it conforms to the provisions of this act and rules and regulations hereunder.
All agreements made in accordance with the provisions of this section shall be on a form prescribed by the department, signed by all parties in interest, and a copy or copies thereof forwarded to the department as required by rules and regulations. It shall be the duty of the department to examine the agreement to determine whether it conforms to the provisions of this act and rules and regulations hereunder.
All notices of compensation payable and agreements for compensation and all supplemental agreements for the modification, suspension, reinstatement, or termination thereof, and all receipts executed by any injured employe of whatever age, or by any dependent to whom compensation is payable under section three hundred and seven, and who has attained the age of sixteen years, shall be valid and binding unless modified or set aside as hereinafter provided.
77 P.S. § 731