For detailed descriptions and animated examples, click on the transaction numbers in the chart below (if you have a dial-up Internet connection, click here for non-animated versions):

Transactions that Occur Prior to Service:
270 Eligibility Inquiry 271 Eligibility Response
278 Authorization Request 278 Authorization Response
Claim-Related Transactions:
837 Claims 835 Remittance
277U Unsolicited Claim Status Response
Payment-Related Transactions:
835 Remittance EFT Electronic Fund Transfer
Transactions That Can Occur Any Time:
276 Claim Status Inquiry 277 Claim Status Response
The Transaction That Occurs With Every Provider Transaction:
997 Transaction Response

To see what happens when an 837 transaction is sent to a payer, view the following animations (if you have a dial-up Internet connection, click here for non-animated versions):

What Happens When an 837 is Rejected?
What Happens When an 837 is Pended?
What Happens When an 837 is Paid?

For more information about HIPAA Transactions, click on the link below:

Decoding the HIPAA Transactions