How to ratify a contract by cashing a check

Uretek USA developed a process for pavement repair, which it sublicensed to Uretek Mexico under an agreement signed in 2003.  In 2010, the principals of the two companies met to try and resolve disputes about that agreement and other business dealings. During the meeting, the parties initialed an amended sublicense agreement, and Uretek USA accepted four checks from Uretek Mexico with these amounts and memo lines:

1. $10 “As per First Amendment to Sublicense Agreement”
2. $76,950.90 for “Full Payment on Technical Assistance”
3. $225,471.05 for “Full Payment on Royalties”
4. $10 for “Full Release [Uretek USA] to [Uretek Mexico]

Uretek USA later sued to dispute the enforceability of the amendment.  The jury found that Uretek USA ratified it by conduct, principally by cashing these checks.  While Uretek USA made several arguments against that finding on appeal, the number of checks and specificity of the notations on them was sufficient to sustain the verdict.  Uretek (USA), Inc. v. Ureteknologia de Mexico S.A. de C.V., No. 13-20430 (Oct. 29, 2014, unpublished).