Agreement can mean simply concurrence among two or more people. For example, my friends might say, “There is general agreement among us that Joel has proven himself to be a complete imbecile by undertaking his Words Project, which is not to say that there weren’t already strong indicators of that before then.” Yeah, my friends are like that.
Agreement might not refer to concurrence among people, but rather the concurrence of, say, documents. For example, newspapers might report that “The offender is in jail due to a lack of agreement between the documents he filed with the tax department and his real financial statements.”
As an honest taxpayer who wouldn’t have to pay as much as I do if everyone paid his or her due, I’m glad they caught the crook. I hope they also extracted a huge fine from him.
An agreement can also be a formal, legally binding contract. Depending on the nature of the agreement, you might find yourself sharing a cell with your tax-scofflaw friend if you willfully break it and refuse to make good on it.