OPINION BY
Judge SIMPSON.Rita Farner (Claimant) petitions for review of an order of the Workers’ Compensation Appeal Board (Board) which declined to set aside a Compromise and Release Agreement (C & R Agreement). The sole issue on appeal is whether Claimant’s mistake provides a sufficient basis to set aside the C & R Agreement. Concluding it does not, we affirm.
In August 1988, Claimant suffered a work-related fractured left arm for which Rockwell International Corp. (Employer) issued a Notice of Compensation Payable. WCJ’s Op. of 2/22/99, Finding of Fact (F.F.) No. 1.
Approximately eleven years later, Employer filed a modification petition, alleging Claimant failed to pursue available work in good faith. Hearings ensued.
During the modification proceedings before a Workers’ Compensation Judge (WCJ), the parties and their lawyers pre-_ sented the C & R Agreement and Stipulations for approval. The C & R Agreement indicated Claimant received a total of $220,905.30 in weekly disability benefit payments and an additional $21,183.56 in medical benefits. Employer agreed to a resolution of the modification petition if Claimant agreed to release all claims related to her work injury in exchange for an additional lump sum payment of $45,000.00. Hearing of 9/4/03, Claimant’s Exhibit 1.
At a hearing to approve the Agreement (Approval Hearing), Claimant responded to questions from her attorney as to her understanding of the C & R Agreement. Especially material for current purposes, Claimant testified that in addition to waiving all workers’ compensation benefits, she resigned her employment. Reproduced Record (R.R.) at 30a. She testified that she would still be entitled to receive her pension from Employer and to receive medical benefits under Employer’s plan. Id. No further information on this point was offered. However, in a written Voluntary Resignation Statement dated the day of the Approval Hearing and received during subsequent proceedings, Claimant explained, “I fully realize that with this resignation, I am no longer entitled to any of the privileges or benefits to which employees of [Employer] may be entitled except those benefits and rights which are vested at the time of my resignation.” R.R. at 20a.
Finding Claimant fully understood the legal significance of the C & R Agreement, the WCJ approved it. Neither party appealed.
Nearly a year and half later, Claimant’s new lawyer filed a review petition alleging Employer breached the C & R Agreement by failing to pay her medical insurance premiums following the WCJ’s approval of the Agreement. WCJ’s Op. of 9/4/03, F.F. No. 3. Employer filed a timely answer maintaining the C & R Agreement did not provide for ongoing medical insurance.
At a hearing before a different WCJ on Claimant’s review petition, Claimant testified that when she settled her case, her former attorney assured her she would continue to receive health care benefits through Employer’s plan. WCJ’s Op. of 9/4/03, F.F. No. 7. Importantly, Claimant did not testify that any representative of Employer discussed this aspect of the settlement with her. Also, Claimant offered copies of the C & R Agreement and Stipulations into evidence.
Thereafter, Employer offered Claimant’s Voluntary Resignation Statement. *1077No testimony by a representative of Employer was received.1
The WCJ set aside the C & R Agreement. In doing so, the WCJ found that the documents did not expressly state that the Claimant would or would not be entitled to ongoing medical insurance coverage. WCJ Op. of 9/4/08, F.F. Nos. 8, 9, 10. He also made the following relevant findings:
11. Based upon my review and consideration of the claimant’s testimony at the February 4, 1999 hearing, and her testimony at the October 29, 2001 hearing, I find that at the time she executed the Compromise and Release Agreement and requested approval of that agreement in February, 1999, it was the understanding of the claimant, Rita Famer, that her medical insurance coverage through United Health Care was going to continue.
I further find the fact that none of the attorneys present at the February 4, 1999 hearing indicated on the record at the February 4, 1999 hearing that the claimant had an erroneous understanding concerning her entitlement to ongoing medical insurance coverage, contributed to the claimant’s belief that she was going to continue to receive ongoing medical insurance coverage through United Health Care.
12. Based upon my review and consideration of all of the evidence and arguments presented in this matter, I find that the claimant, Rita Famer, had a mistaken understanding as to whether her medical insurance coverage with United Health Care was going to continue following the approval of the Compromise and Release Agreement the parties entered into on February 4, 1999. I further find, given the claimant’s testimony at the hearing of October 29, 2001 and given the filing of her Review Petition, that it was important to the claimant that her medical insurance continue, and that she would not have entered into the Compromise and Release Agreement if she knew that her medical coverage was going to cease. I thus find that there was a clear misunderstanding/mistake pertaining to a material issue at the time the parties executed the Compromise and Release Agreement of February 4, 1999, and at the time they asked for it to be approved. As such, the Compromise and Release Agreement must be set aside.
WCJ’s Op. of 9/4/03, F.F. Nos. 11, 12 (emphasis added).
Employer appealed to the Board, which reversed, holding the WCJ erred in setting aside the C & R Agreement. The Board reasoned that Claimant genuinely misunderstood the Agreement, but it noted her written acknowledgement in the Voluntary Resignation Statement. Board Op. at 5, 6. The Board concluded Claimant’s misunderstanding was a unilateral mistake insufficient to set aside the C & R Agreement. Board Op. at 6. This appeal followed.2
On appeal, Claimant argues the Board erred because she established the Agreement was materially incorrect. She also *1078relies on the doctrine of mistake. In particular, she contends that Employer was aware of her mistake at the time she signed the C & R Agreement but did nothing to dispel her misunderstanding. She further claims Employer’s silence at the Approval Hearing proves mutual mistake.
Section 449 of the Workers’ Compensation (Act),3 77 P.S. § 1000.5, governs the compromise and release of workers’ compensation claims. This section provides that settlement agreements are not valid or binding until approved by a WCJ. Id. Further, “[t]he [WCJ] shall not approve any compromise and release agreement unless he first determines that the claimant understands the full legal significance of the agreement.” 77 P.S. § 1000.5(b). Once approved, a valid compromise and release agreement is final and binding on the parties. Pimentel v. Workers’ Comp. Appeal Bd. (United Neighborhood Ctrs. of Lackawanna County), 845 A.2d 234 (Pa.Cmwlth.2004).
Over the past year this Court dealt with several attempts to set aside C & R agreements. Two different analyses emerged. First, the Court utilized a common law standard for setting aside a C & R agreement, so that such an agreement can be set aside only upon a clear showing of fraud, deception, duress or mutual mistake. N. Penn Sanitation, Inc. v. Workers’ Comp. Appeal Bd. (Dillard), 850 A.2d 795 (Pa.Cmwlth.2004).4
More recently, the Court expressed the view that the unappealed approval of a C & R agreement precludes re-litigation of the required finding that the claimant understood the full legal significance of the agreement. Stiles v. Workers’ Comp. Appeal Bd. (Dep’t of Pub. Welfare), 853 A.2d 1119 (Pa.Cmwlth.2004)(en banc), appeal denied, — Pa. -, — A.2d -, 2005 WL 562498 (426 WAL 2004, filed December 16, 2004). See also N. Penn Sanitation (concurring opinion, Leadbetter, J.). Under a collateral estoppel analysis, a party is foreclosed from re-litigating an issue of law or fact when the following factors are demonstrated: (1) the legal or factual issues are identical; (2) they were actually litigated; (3) they were essential to the judgment; and (4) they were material to the adjudication. Stiles. As this more recent analysis was adopted by the majority of an en banc panel of this Court, we will apply it here.
Applying the collateral estoppel analysis, there is no question that all necessary elements for preclusion are present. The factual issue raised here, mistake as to understanding the full legal significance of the Agreement, was decided in the earlier litigation. The issue was actually litigated, it was essential to approval of the C & R Agreement, and it was material to the approval of the Agreement.
Claimant argues that she is entitled to relief under the doctrine of mutual mistake. However, even if she could re-litigate her understanding of the Agreement, Claimant would not prevail on this theory.
Compared to fraud, deception or duress, the test to set aside a C & R agreement on the basis of mutual mistake is more stringent. N. Penn Sanitation. Thus, in order for mutual mistake to con*1079stitute a basis for invalidating a C & R agreement, the party seeking to set aside the agreement must prove both parties are mistaken as to a present, material fact that existed at the time the agreement was executed. Id.
Here, Claimant proved that she signed the C & R Agreement while under a mistake as to Employer’s duty to continue paying medical insurance premiums after her resignation. However, the WCJ made no finding that Employer shared that mistake at the critical time. Given that no Employer witness testified, this lack of finding concerning Employer’s state of mind is not surprising. The absence of any finding as to Employer’s state of mind results in the conclusion that Claimant failed to prove mutual mistake.5
Claimant raises several interesting arguments inviting a re-weighing of the circumstantial evidence so as to support an inference of Employer’s knowledge. However, arguments as to the weight of evidence are for the fact-finder, not this Court. Universal Cyclops Steel Corp. v. Workmen’s Comp. Appeal Bd. (Krawczynski), 9 Pa.Cmwlth. 176, 305 A.2d 757 (1973).
Also noteworthy are the WCJ’s findings that the documents do not expressly state that the Claimant would or would not be entitled to ongoing medical insurance coverage after her resignation. Significantly, there was no finding that the C & R Agreement promised continued payment of the medical insurance premium, and there was no conclusion of law that Employer breached the C & R Agreement. Moreover, there was no effort by Claimant to prove that medical insurance coverage was a vested benefit, the continuation of which was memorialized in her Voluntary Resignation Statement.
Finally, we reject Claimant’s arguments that her review petition should be granted. Section 413(a) of the Act, 77 P.S. § 771, permits a WCJ to review an original or supplemental agreement if it be proved that it was in any material respect incorrect.6 However, in the absence of a finding that the C & R Agreement was incorrect when executed and that the parties intended different terms, Claimant here cannot obtain the relief she seeks under this theory.
Given the foregoing discussion, we affirm.
*1080 ORDER
AND NOW, this 9th day of February, 2005, the order of the Workers’ Compensation Appeal Board is AFFIRMED.
. At one point, Employer offered an affidavit from an out-of-state representative of Employer, but Claimant’s hearsay objection was sustained.
. Our review is limited to determining whether an error of law was committed, whether necessary findings of fact are supported by substantial evidence or whether constitutional rights were violated. Johnson v. Workers’ Comp. Appeal Bd. (Abington Mem’l Hosp.), 816 A.2d 1262 (Pa.Cmwlth.2003).
. Act of June 2, 1915, P.L. 736, as amended, 77 P.S. § 1000.5, added by the Act of July 2, 1993, P.L. 190.
. See also Barszczewski v. Workers’ Comp. Appeal Bd. (Pathmark Stores, Inc.), 860 A.2d 224 (Pa.Cmwlth.2004)(need not decide whether res judicata properly applied because underestimating damages does not amount to mutual mistake).
. Claimant also argues she is entitled to relief under the doctrine of unilateral mistake. We disagree on legal and factual grounds. Legally, collateral estoppel applies and precludes re-litigation of the prior finding that Claimant understood the full legal significance of the C & R Agreement. Factually, unilateral mistake supporting relief was not proven. Generally, a unilateral mistake which is not caused by the fault of the opposing party affords no basis for relief. Welsh v. State Employees’ Retirement Bd., 808 A.2d 261 (Pa.Cmwlth. 2002). However, "[i]f a party to a contract knows or has reason to know of a unilateral mistake by the other party and the mistake, as well as the actual intent of the parties, is clearly shown, relief will be granted to the same extent as if a mutual mistake existed.” Id. at 265. See also Growth Horizons, Inc., v. Workers' Compensation Appeal Bd. (Hall), 767 A.2d 619 (Pa.Cmwlth.2001). Claimant here failed to present any evidence of Employer’s intent, and the WCJ made no finding as to Employer's intent. Without supporting evidence and a finding of actual intent, it is impossible for Claimant to carry her burden under the doctrine of unilateral mistake.
. Cf. Wallace v. Workers’ Comp. Appeal Bd. (Bethlehem Steel), 854 A.2d 613, 620 at n. 10 (Pa.Cmwlth.2004)(using Section 413(a) review to resolve ambiguity in scope of C & R agreement). But see N. Penn Sanitation (Section 413(a) does not authorize setting aside a C & R agreement).