Payment posting in medical billing is where underpayments are either caught or lost. A payment posted as a lump sum against a balance hides the line that paid short, the line that was denied and the line where the payer quietly moved the balance to the patient. Posting is the least visible step in the cycle and the one that decides whether every step after it is working from true numbers.
Posted at the line, not the total
Electronic remittance advice arrives as an 835 file and is posted line by line with every CARC and RARC code intact. Auto-posting handles the volume, but each batch is reviewed, because auto-posting will happily book a CO-45 contractual adjustment that is really a short pay. Paper EOBs are keyed the same way, with the same codes. This is what makes it possible to see that a claim was paid but paid less than the contracted rate, or that a 99214 was reduced to a 99213 under CO-97, which a lump-sum posting simply cannot show.
Reconciled against the bank
Each posting batch is closed against a specific deposit amount, so the day's posting either balances to the bank or a discrepancy is logged for follow-up. Electronic payments are matched to the 835 by the trace number, paper checks by check number and lockbox date. A remittance with no deposit, or a deposit with no remittance, is chased that week. Discrepancies get investigated rather than adjusted away, because a missing deposit that gets written off as a small variance is money that never arrived.
Underpayments and adjustments that need a second look
With your fee schedules loaded as expected amounts, line-level posting makes contractual underpayments visible the day they post. It also surfaces the adjustments that deserve a question. A PR-1 deductible or PR-2 coinsurance on a patient who has a secondary means the secondary needs a claim, not the patient a statement. An OA-23 on a Medicare secondary line needs checking against the primary's payment. A CO-18 duplicate may mean the original was paid and this is a takeback, or that a corrected claim went out without frequency code 7. Each of these becomes a work item with the expected amount and the difference recorded instead of quietly becoming your write-off number.
The daily payment posting cycle
Electronic remittances arrive through your clearinghouse and are posted the day they land. Paper EOBs and patient payments are posted on the same schedule from your lockbox, scanned mail or front-desk batch. Zero-pay remittances are posted too, carrying their CO-16, CO-29 or CO-197 reason, because a denial that never gets posted never reaches denial management. Unapplied payments, where the remittance cannot be matched to a claim, are worked from a list rather than left in suspense. The weekly report shows posted totals by payer, unapplied balances, open deposit discrepancies and the underpayment list.
What payment posting feeds downstream
Posting sets the starting point for three other services. Every denied or reduced line becomes a work item for denial management, carrying its CARC and RARC codes as the payer sent them. Every claim posted short of the contracted rate becomes an underpayment item for A/R follow-up, with the expected amount and the difference recorded. And every line where the payer moved the balance to the patient becomes a statement line in patient billing, which is why a posting error shows up as a confused patient a month later. If posting is late or lump-sum, all three of those queues are wrong, and the aging report your account manager reviews with you is describing money you already have.
Checking whether your payments are really being reconciled
Take one week of deposits from your bank statement and ask for the posting batches that account for each one. If the batches cannot be matched to deposits, reconciliation is not happening, whatever the vendor calls it. Look at a sample of remittances and check that the adjustment codes on the posting match the codes on the remittance line by line rather than a single contractual adjustment covering the whole claim. Ask for the unapplied cash list and how old the items on it are. Ask how many claims were flagged as underpaid last month; a vendor that reports none either has perfect payers or is not comparing paid amounts against your fee schedule.
What Is Included
- 835 ERA auto-posting reviewed line by line, paper EOBs keyed the same way
- CARC and RARC codes kept on every adjusted line
- Each batch balanced to a specific bank deposit
- Allowed amounts compared to your contracted rate
- Zero-pay remittances posted so denials reach follow-up
| Adjustment code standard | CARC and RARC codes maintained by X12 explain every payer adjustmentSource: X12, Claim Adjustment Reason Codes |
|---|---|
| Electronic remittance standard | The HIPAA-adopted electronic remittance advice is the ASC X12 835 transaction, and health plans must use CARC and RARC codes to explain adjustmentsSource: CMS, EFT and ERA transactions |
| Remark code list | RARC codes such as MA130 and N4 are published and updated by X12Source: X12, Remittance Advice Remark Codes |
Payment Posting & Reconciliation: Common Questions
Yes, both. Front-desk, mailed and online patient payments are posted to the specific charge they were meant for on the same cycle as insurance payments, so the balance a patient sees on a statement reflects everything received.
It is flagged as an underpayment and worked rather than adjusted off under CO-45. Catching these consistently depends entirely on posting at the line level with the expected amount loaded in your system.
On the same cycle they are received, usually the day the 835 lands in the clearinghouse, because unposted payments make your aging report wrong and send your follow-up team after money you already have.
Yes, or at least the fee schedule from each contract loaded into your system. Without the expected amount there is nothing to compare the payment against. Where contracts are missing, we tell you which payers cannot be checked.
It is posted to unapplied cash and worked from a list, starting with a call to the payer or a check against the remittance. It is not left in suspense or applied to the oldest balance to make it disappear.
Because paid is not the same as paid correctly. A short pay, a balance moved to the patient under PR-1 or PR-2 when a secondary should have been billed, or a takeback hidden in a later remittance only shows up if each line is posted with its reason code.