There is a known issue where users are unable to save changes that they have made to the tax information fields (tax amount, assessment, mil rate and tax year) on Incomplete listings. Matrix will allow the user to make the change and save it as INC, but the fields actually never change. The data that was in the fields (that filled in from the tax record) prior to the agent updating it remains, even though it looks like the updated information was saved successfully.
To get around this and enter the correct information, you must first submit the listing as Active. Once the listing is Active, you will be able to go back into the listing, make the changes to the tax information and save them.