An MOA or PA is a legally binding document that commits an agency both by statute and by federal regulation to carry out the undertaking in accordance with the terms of the agreement in satisfaction of its responsibilities under Section 106. The MOA or PA serves three main purposes: (1) to specify the alternatives or mitigation agreed to by the signatories; (2) to identify who is responsible for carrying out the specified measures; and (3) to serve, along with its implementation, as evidence of the agency's compliance with Section 106 of the NHPA.

Signatory Status

Parties who may sign a MOA or PA fall into one of three categories: (1) signatories; (2) invited signatories; and (3) concurring parties.

Signatory: In accordance with 36 CFR § 800.6(c)(1), a signatory has the sole authority to execute, amend, or terminate the agreement. The federal agency and the SHPO/THPO are signatories; the ACHP is a signatory as well when it has participated in consultation for the agreement and in all program PAs. Except as described below, their signature is almost always required for the agreement to go into effect. A THPO or other tribal representative is a required signatory to a Section 106 agreement only when an undertaking may occur on, or affect historic properties on, tribal lands. Once all of the signatories have signed the agreement, it is executed and goes into effect.

Federal agency: The federal agency official, as defined by 36 CFR § 800.2(a), is the person who signs the agreement on behalf of the agency. A federal agency is not required to sign a Section 106 agreement for an undertaking where, pursuant to 36 CFR § 800.2(a)(2), another federal agency has agreed to act as "lead agency" on its behalf. In such an instance, the lead agency signs the Section 106 agreement on behalf of the non-lead agency to fulfill their collective responsibilities for the undertaking. Where the agencies have chosen to designate one agency as lead for the purposes of Section 106 review, the ACHP strongly encourages the agencies to evidence this lead agency agreement in writing since the lead federal agency is being given the authority to potentially commit other agencies to a course of action. The existence of such lead agency agreements should be noted in the preamble of the Section 106 agreement. If the non-lead federal agency has specific duties in the MOA or PA, they should be an invited signatory to the agreement.

SHPO/THPO: The SHPO/THPO or their designee is usually the individual who signs the agreement on behalf of the SHPO's office or the THPO's office. When the subject undertaking of an agreement will occur on or affect historic properties on tribal lands and there is no THPO designated under Section 101(d)(2) of the NHPA (54 U.S.C. § 302702), a representative designated by the tribe shall sign the agreement as a signatory in addition to the SHPO.

ACHP: If the ACHP participates in the consultation to develop the agreement, it also signs the MOA or PA as a signatory. When the ACHP is participating in consultation, usually the executive director of the ACHP is the individual who signs the agreement on behalf of the ACHP. In certain situations, the chairman of the ACHP may sign the agreement for the ACHP.

Invited signatory: In accordance with 36 CFR § 800.6(c)(2), an invited signatory, upon signing, has the authority to amend and terminate the agreement. The agency official may invite additional parties to sign the agreement, such as an Indian tribe or NHO who attaches religious and cultural significance to historic properties affected by the undertaking (off tribal lands), or any party that assumes a responsibility under the agreement. The refusal of an invited signatory to sign the agreement does not prevent the agreement from being executed; however, an agreement cannot impose a duty or responsibility on a party that has not signed it. When an Indian tribe or NHO is asked to be an invited signatory to an agreement for which the undertaking will not occur on or affect historic properties on tribal lands, the THPO or a representative designated by the tribe or NHO, as the case may be, can sign the agreement on behalf of the tribe or NHO. The ACHP notes and accepts that some tribes may decline to sign agreement documents in principle but may participate in development of the agreement. Such decisions are within the rights of Indian tribes, and the ACHP recommends that agencies understand and accept such decisions.

Applicants are frequently asked to be invited signatories due to the responsibilities assigned to them under the agreement. In some instances, an agency may be able to condition the terms of its assistance or permit to an applicant as a means of compelling the applicant to take certain actions under a Section 106 agreement even if the applicant declines to sign the agreement. Federal agencies determine whether to invite additional signatories to sign the agreement and should weigh the decision carefully, since an invited signatory who actually signs an agreement has the same ability to amend or terminate the agreement as other signatories. Asking parties to be invited signatories to a Section 106 agreement can evidence a higher level of commitment to success in the agreement's implementation as well as continued engagement and partnership in the process.

Concurring party: In accordance with 36 CFR § 800.6(c)(3), a concurring party is a consulting party invited to concur in the agreement document but who does not have the authority to amend or terminate the agreement. Like an invited signatory's signature, a concurring party signature is not required to execute the agreement; a concurring signature is essentially an endorsement of the agreement. Thus, the refusal to sign by any party asked to concur in the agreement does not prevent the agreement from being executed. Whether any or all other consulting parties are invited to concur in an agreement is at the federal agency's sole discretion. Extending the offer to sign an agreement as a concurring party may be an effective way of recognizing the assistance and support that a party has provided for the actions being evidenced in the agreement and encouraging their ongoing support.

The individual who signs the agreement on behalf of any invited signatory or concurring party should be one with approval authority for any responsibilities or duties assumed under the agreement, or authority to represent the broad interests of their organization, as the case may be. The signature page of the agreement document should identify and differentiate the signatories, invited signatories, and concurring parties.


To execute an agreement, the federal agency and the SHPO/THPO (and the ACHP if participating, and in all program PAs) sign and date the agreement. Once so signed, the agreement is executed. The federal agency can seek the signatures of any invited signatories and concurring parties, but such an agreement is already executed and in effect. Pursuant to 
36 CFR § 800.6(b)(1)(iv), the agency official must submit a copy of the executed agreement, along with the documentation specified in 36 CFR § 800.11(f), to the ACHP prior to approving the undertaking. The ACHP does not need to receive an original copy of the agreement; a scanned PDF or mailed copy is sufficient provided its text, all signatures, and any attachments (e.g., exhibits, appendices -- in color if necessary) are clear. The agency official should also send copies of the fully executed agreement to all the consulting parties.

When the ACHP is participating in the consultation process, it should be the last signatory to sign the agreement. The federal agency should sign the agreement first, and seek the signature of the SHPO/THPO, and invited signatories who will be assuming responsibilities under the agreement prior to sending it to the ACHP for execution. After the ACHP signs, the agreement is in effect, and the agency can then circulate it for the signatures of those invited signatories who do not have responsibilities under the agreement and concurring parties. While the ACHP prefers to receive the original document, in some situations it may advise that an electronically mailed PDF or mailed hard copy with the other signatures will suffice. The agency should work with the ACHP staff contact regarding the form and transmittal of the signature copy. Once the ACHP, agency, and SHPO/THPO have signed the agreement, it is executed. The ACHP will retain a copy of the signed agreement for its records. The process for executing PAs is the same as the process for executing MOAs.

Once the federal agency has a fully executed Section 106 agreement in place, in addition to providing copies to all the consulting parties, it should make this information available to the public, subject to the confidentiality provisions in 36 CFR § 800.11(c). The agency must then ensure the undertaking is carried out in accordance with the terms of the agreement.

Advisory Comments

In some situations, the ACHP may determine it is appropriate to provide additional advisory comments about an undertaking for which an agreement will be executed. In this situation, the ACHP shall provide its comments to the agency official in writing when it executes the agreement. In such circumstances, the ACHP will typically ask that the agency official ensure all consulting parties are provided with the ACHP's comments.

Signing Agreements in Counterpart

Section 106 agreement documents may be executed in counterparts; i.e., each signatory, invited signatory, and concurring party may sign and date a separate signature page concurrently or sequentially that are then attached together to make up a single agreement with all signatures. In this situation, each separate signature page should include the complete title of the agreement so there is no ambiguity about what document the party is signing. For an example of a properly formatted counterpart signature page, click here.


If an MOA or PA needs to be amended, the changes are recorded in a format that looks just like the MOA format. Amendments are executed in the same manner as the original agreement. Once an invited signatory signs the original Section 106 agreement, that invited signatory must also sign the corresponding amendment to make it effective. Therefore, the same signatories and invited signatories sign the amended agreement, and a fully executed copy is filed by the agency (with any attachments, exhibits, appendices -- in color if necessary) with the ACHP.