Code 87 is used as a catch-all for a variety of deduction issues. Look at your claim copy for an explanation of how it is being applied in your situation. Backup can be requested by submitting the backup request form found on Retail Link.
A common example of a code 87 is Walmart sending over one big bucket of invoices that have not yet been paid, like a year's worth of damaged/defective codes rather than sending over an individual deduction for each one. You should always request more information by submitting the backup request form found on Retail Link when you receive a code 87 so that you can see what can be disputed.
How to Prevent Valid Code 87s
Since code 87s could represent any number of claim reasons, there is not a good way to prevent these.
Can it be Disputed?
Depending on the reason for the Code 87, it may be able to be disputed. First, request backup documentation by submitting the request for backup form found on Retail Link.