Understanding ERA 835: A Practical Guide for Therapists

Key Takeaways

• An ERA 835 is the electronic payment explanation that insurance companies send to providers after they process a claim. An EOB is the related document that usually goes to the client.
• ERAs show what was paid, what was adjusted, what the client owes, and why.
• ERAs don't show up automatically. You usually need to enroll with each payer, often through your clearinghouse.
• Adjustment codes like CO-45, PR-3, and CO-16 each mean something specific and call for a specific next step.
• Auto-posting ERAs saves time, but it still needs regular spot checks to catch underpayments.

You open your billing dashboard and see a payment of $88 for a session you billed at $175. Did you get shortchanged? Is something wrong? Do you need to call someone?

Probably not. But the answer is sitting in your ERA, and knowing how to read it is one of the most useful billing skills a therapist can have.

ERA 835s look intimidating, but they follow the same pattern every time. Below, you'll find what they are, how to read one, what the most common codes mean, and what to do when something looks off.

What Is an ERA 835?

ERA stands for electronic remittance advice. It's the document an insurance company sends you after it processes (or "adjudicates") a claim. Think of it as the insurer's receipt: what they paid, what the client owes, what got adjusted, and why.

The 835 is the name of the standard HIPAA format for electronic remittance. Because every payer uses the same format, your billing software can read payment data from lots of different insurers without you reformatting anything.

You'll almost never see a raw 835 file, which looks like a wall of code. Instead, your clearinghouse receives it from the payer and passes it to your EHR or billing software, which turns it into a readable payment report. When you open a payment and see line items showing what an insurer paid for each session, that's the 835, dressed up for humans.

ERA vs. EOB: What's the Difference?

People use these terms interchangeably, but they're not quite the same:

Heads up: clients may get a paper EOB in the mail even though you already received and posted the ERA. That's how you end up with a confused client calling to say "My insurance sent a letter saying I owe money." Both documents are correct. A quick explanation at intake saves everyone a headache.

If you're set up to receive ERAs (see how to enroll) but a payer keeps sending paper, check with your clearinghouse. Paper means manual entry, and manual entry means more room for mistakes.

How to Read an ERA 835

Once you know the key fields, ERAs get a lot less intimidating:

• Billed amount: what you charged for the session.
• Allowed amount: the rate your contract with the payer allows.
• Paid amount: what the insurer actually sent you. Usually the allowed amount minus the client's share.
• Patient responsibility: what the client owes, like a copay, coinsurance, or deductible.
• Contractual adjustment: the difference between what you billed and the allowed amount. This is a write-off, not a denial.
• Claim status: whether the claim was paid, denied, or adjusted. Your first stop when reviewing.
• Service line detail: when a payer bundles several sessions into one payment, this breaks out each date of service. Always reconcile line by line. The total alone can hide a problem.

Example: Reading an ERA for a 90837 Session

Here's a fictional example for one 90837 session (60-minute psychotherapy):

The math should always balance:

Billed amount = Paid amount + Patient responsibility + Adjustments

$175.00 = $88.00 + $22.00 + $65.00 ✓

What to do with each number:

1. Post $88.00 as the insurance payment.
2. Apply the $65.00 CO-45 as a contractual write-off.
3. Move the $22.00 copay to the client's balance.

The CO-45 is just the gap between your fee and the rate you agreed to when you joined the network. No follow-up needed.

If the math on a real ERA doesn't balance, pause before posting. Something was handled incorrectly somewhere, and it's much easier to sort out now than later.

ERA Adjustment Codes for Mental Health Claims

Adjustment codes are the insurance company's explanation for every dollar that didn't land the way you expected. There are two main types, both maintained by X12:

• Claim adjustment reason codes (CARCs) explain why a payment was reduced or denied.
• Remittance advice remark codes (RARCs) add extra detail. Think of CARCs as the "what" and RARCs as the "what now."

Every CARC comes with a group code that tells you who's responsible for the amount:

• CO (contractual obligation): you write it off. You can't bill the client for it.
• PR (patient responsibility): the client owes it.
• OA (other adjustment): used when no other group applies. Common with coordination of benefits.
• PI (payer initiated): the payer made the adjustment under its own policy. Medicare doesn't use this one.

One quirk: the payer assigns the group code, so the same reason code can show up with a different prefix depending on the payer and situation.

Common CARCs in Therapy Billing

Two codes to watch closely in behavioral health: CO-119 (benefit maximum) and CO-197 (authorization). Mental health benefits often come with session limits and authorization requirements. When these codes show up, the fix is sometimes a conversation with the client about their remaining benefits, or an appeal for continued care.

How to Enroll in ERA 835

Here's something many therapists find out the hard way: enrolling to submit claims electronically is separate from enrolling to receive ERAs. You can be fully set up to send claims and still get paper for every payment, just because the ERA step never happened.

There are two main ways to enroll:

• Through your clearinghouse. This is the most common route for therapists. Many clearinghouses let you request ERA enrollment for each payer and handle the connection for you.
• Directly with the payer. Some payers handle ERA enrollment through their own provider portals. Check each payer's portal or ask your clearinghouse which route applies.

A few practical tips:

• Start early. If you're newly joining insurance networks, request ERA enrollment at the same time as electronic claims enrollment. Activation can take several weeks, and you'll be stuck with paper until it's done.
• Not sure if you're enrolled? Ask your clearinghouse. They can usually check your status with each payer quickly.

ERA Reconciliation: A Simple Workflow

You don't need a billing department to keep your books clean. Here's a workflow that works for solo and small practices:

1. Open the new ERA in your billing software.
2. Match each line to a claim. Check the client name, date of service, and CPT code. A mismatch usually means a data entry error or a payer processing error.
3. Check the math. Does the paid amount equal your contracted rate minus the client's share? If you expected $88 and got $80, flag it before posting.
4. Post everything. Insurance payment, write-offs, and client balance. Every line should be fully resolved.
5. Flag denials and short payments right away. Appeal and resubmission deadlines vary by payer, so check your contracts and don't let these sit.
6. Match ERAs to your bank deposits regularly, like once a week. If they don't line up, the issue is often a clearinghouse glitch or a payment delay.

ERA Auto-Posting: Helpful, With a Catch

Auto-posting means your billing software applies ERA payments to claims automatically, without you reviewing each line. For a busy caseload, that can save a lot of time.

The catch: auto-posting only knows what you tell it. If your contracted rates aren't set up correctly in your system, it can't flag a payment that comes in short. It'll just post whatever the ERA says, and underpayments can slip by for months.

To use auto-posting safely:

• Enter your fee schedules accurately for each payer before turning it on.
• Spot-check regularly. Once a month, compare expected rates to what actually posted for a handful of claims.
• Review denials and remark codes by hand, even if auto-posting handles the rest.
• Double-check that client balances are separated from insurance payments correctly.

What to Do When an ERA Shows a Problem

Denials

A denied claim shows a $0 payment and one or more CARCs explaining why. Your next step depends on the code:

• OA-18 (duplicate): check whether you really submitted twice. If the first claim paid, close out the duplicate.
• CO-11 (diagnosis doesn't match procedure): review the ICD-10 code, correct it, and resubmit.
• CO-16 (missing information): check the paired remark code to find what's missing, then fix and resubmit.

The big rule: don't resubmit a denied claim without fixing the reason it was denied. Sending the same claim again usually just gets the same denial. For more on this, see our guide to insurance claim denials.

Payments Below Your Contracted Rate

These are sneakier than denials, because everything looks fine until you check the numbers. Compare the allowed amount on the ERA to your contract. If it's lower, you've found an underpayment. Write down the details, call the payer's provider line with your contract rate and ERA info handy, and ask for a corrected payment.

Authorization Denials

These are common in behavioral health, partly because some plans hand off mental health benefits to a separate behavioral health company. When you see an authorization-related code, check:

• The authorization number you have on file
• Whether you've gone over the approved number of sessions
• Whether the dates of service fall inside the authorization period

If everything looks right on your end, call the payer. If the denial is about medical necessity, you can usually appeal with clinical documentation.

Missing ERAs

If a claim has been out for a while and no ERA has arrived, start with your clearinghouse. Confirm the claim was sent and accepted. If it was, call the payer and ask for the claim status. Sometimes claims just get stuck, and a phone call is the only way to unstick them.

ERAs and Secondary Insurance

If a client has two plans, the primary plan's ERA is only step one. 

After you post the primary ERA, check whether the client has secondary coverage before closing out the claim. The primary ERA shows the secondary plan exactly what was paid, what was adjusted, and what the client still owes. On the secondary plan's ERA, you'll often see OA-23, which reflects the prior payer's payment.

Medicare crossovers: when Medicare is primary, it can automatically forward ("cross over") the claim to a supplemental plan or Medicaid. The Medicare ERA usually includes a remark code saying the claim was forwarded (Medicare uses MA18 for this). If you see it, check with the secondary payer before submitting again so you don't create a duplicate.

It's easy to skip secondary billing because each payment feels small. But it adds up. As a hypothetical, a $22 secondary payment for 10 clients a week over 50 weeks comes to $11,000 a year.

Reading and reconciling ERAs takes time you'd probably rather spend with clients. With Blueprint's all-in-one EHR, you can submit claims, enroll in ERAs, and track insurance payments in one place, and when a denial comes in, Blueprint can draft the appeal for you. See how Blueprint works.

For more billing basics, check out our mental health billing guide.

ERA 835 FAQ

What is an ERA 835 in mental health billing?

An ERA 835 is the electronic payment explanation an insurance company sends to a provider after processing a claim. The "835" is the standard HIPAA format for it. In your billing software, it shows up as a breakdown of what was paid, what was adjusted, and what the client owes.

What's the difference between an ERA and an EOB?

An ERA is an electronic file sent to your billing system, so it can be posted automatically. An EOB is a human-readable document, usually sent to the client. They share similar payment information, but the details can vary by payer.

What does CO-45 mean on a therapy claim?

CO-45 is a contractual adjustment: the difference between what you billed and your contracted rate. If you bill $175 and your contracted rate is $110, the $65 difference shows up as CO-45. It's not a denial, and you just post it as a write-off.

How do I enroll to receive ERAs?

ERA enrollment is separate from electronic claims enrollment and usually needs to be done for each payer. Most therapists enroll through their clearinghouse. Some payers handle it through their own provider portals. It can take several weeks to activate.

What should I do if an ERA payment is less than my contracted rate?

Compare the allowed amount on the ERA to your contract. If it's lower, call the payer's provider line with your contract rate and ERA details, document the call, and ask for a corrected payment.

Is ERA auto-posting safe?

Yes, as long as your fee schedules are set up correctly in your billing software. Spot-check posted payments regularly and review denials by hand, so underpayments don't slip through.