§ 24-3-2 [Parol Evidence for Incomplete Writings]

When two people make a deal, they do not always write down every single detail. If the written contract was never meant to cover everything, a judge can allow spoken or outside agreements to be brought in as evidence, as long as those agreements do not contradict what was written down.

For example, if a written contract covers the main terms of a sale but leaves out some side agreements, those side agreements can still be presented in court. The key is that the extra information must fill in gaps, not change or cancel out what the writing already says.