Be sure to use the code set that is effective and valid for the date of service the patient was seen or your claim will be denied.You cannot submit ICD-9-CM codes on a claim for any encounter after October 1, 2015.
A claim cannot contain both ICD-9-CM and ICD-10-CM codes, it will be returned as unprocessable.
Do not change the codes on a claim when you re-bill a corrected claim.
If the encounter happened September 30, 2015 or prior you will submit your claims using ICD-9- CM.
If your claim begins on September 30, 2015 and ends on October 1, 2015, you will need to split your claims and send two different claims.
This information and much more can be found in InstaCode Institutes Quick Start Guide