This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
If a dispute of fact arises as to the existence of a new contract, which modifies or abrogates a prior contract, the burden of proof is upon the party who alleges such modification.1 In most jurisdictions it is held or assumed that proof of such contract is sufficient if its existence is established by a preponderance of the evidence.2 In some jurisdictions, however, it is said that the degree of proof to establish a modification of a written contract is as great as is necessary to reform a written contract on the ground of mistake in expression.3 Some of the courts which allow an oral contract to modify a prior written contract, hold that proof of such new oral agreement must be clear.4
5Mettel v. Gales, 12 S. D. 632, 82 N. W. 181.
6Kinsm-an v. Stanhope, 60 Mont. 41; L. R. A. 1916C, 443, 144 Pac. 1083.
7Pearsall v. Henry, 153 Gal. 314, 95 Pac. 154 [judgment affirmed on rehearing, Pearsall v. Henry, 153 Cal. 314. 96 Pac. 159]; Levin v. Hunt, - Okla. - , 172 Pac. 940; Hart v. Frost, - Okla. - , 175 Pac. 257.
1 United States. Cowen Co. v. Houck Mfg. Co., 249 Fed. 285.
Arkansas. Bagnell Tie & Timber Co. v. Goodrich, 82 Ark. 547, 102 S. W. 228.
Colorado. Shulze v. Shea, 37 Colo. 337 [sub nomine, Schulze v. Shea, 86 Pac. 117].
Iowa. Beck v. Umshler, 139 la. 378, 116 N.W. 138.
Pennsylvania. Phillips v. American Cement Tile Mfg. Co., 220 Pa. St. 141, 69 Atl. 589.
2 Bagnell Tie & Timber Co. v. Goodrich, 82 Ark. 547, 102 S. W. 228; Shulze v. Shea, 37 Colo. 337 [sub nomine, Schulze v. Shea, 86 Pac. 117]; Beck v. Umshler, 139 Ia. 378, 116 N. W. 138.
3 Phillips v. American Cement Tile Mfg. Co., 220 Pa. St. 141, 69 Atl. 589.
For the degree of proof requisite in reformation for mistake in expression, see Sec. 2234.
4 Watson v. Janion, 6 Or. 137; Boyes v. Ramsden, 34 Or. 253, 56 Pac. 538; Kent v. Kent (Va.), 34 S. E. 32.