A 1954 letter from the corporate trustee stating that its compensation would be 5% of income was a fee agreement binding the trustee, and the trustee did not provide sufficient evidence that additional compensation should be allowed under 20 Pa.C.S. § 7768(b). The letter did not limit principal commissions, and the trial court did not abuse its discretion in allowing an interim principal commission. Trust under Deed of Wallace F. Ott, 2021 PA Super 203 (10/12/2021), aff’g 10 Fid.Rep.3d 281 (Philadelphia O.C. 2020).