How to know when data is 'right' for its purpose by Annette Wright via @infomgmt

The key to evaluating the accuracy of data is more about understanding the eventual use of it than any arbitrary or independent measure.

I agree with Annette although I would bring your attention to some ways to try and make sure that data is correct. 

1..For codes always provide values to select from - yes you cannot guarantee the value chosen is the right one but it is a major step forward just to ensure that there are a finite list of values for that field.

2. For some fields use publicly available data to try and limit data entry to valid values - examples could be master postal code lists, master lists of registered companies, master lists of ISO values for items like a country number, language code, etc.  Yes you cannot guarantee that the correct value is selected but you can at least make sure that the value selected is from a finite master list AND is a valid value.

3.  Make sure that all customer facing systems give the customer a mandatory chance to check and correct their data.

Update your processes to ensure that system design takes all of these things into account - time for a culture change to make sure data quality is a top priority in your organisation.