Posting a Payer Interest Payment

A claim payment answers a question about the claim: what the payer allowed, what it adjusted, what it paid, and what it left to the patient. A payer interest payment answers a different question entirely — not what the claim was worth, but how long the payer took to pay it. The two amounts arrive together and mean nothing alike. One is the result of adjudication; the other is a penalty the payer pays itself for missing a deadline.

That distinction is the whole of the posting problem. The claim's paid amount is measured against its allowed amount — it describes an adjudication. Interest is measured against a calendar. If interest is folded into the claim's payment, the claim now reads as though the payer allowed and paid more than it did, and nothing downstream can tell the difference: the extra money looks like the service was reimbursed above its contracted rate. The rest of the Payments & Posting section is about recording what the payer decided; interest is the one amount on the remittance the payer did not decide about any claim.

Interest is not a courtesy a payer extends; it is owed under a rule, and which rule depends on the payer. For Medicare fee-for-service, federal statute requires interest on a clean claim that is not paid within the period the law sets, at the rate used for the federal Prompt Payment Act — a rate the U.S. Treasury sets and updates on a schedule, not a figure fixed in the statute. The obligation is durable; the number is not, which is exactly why it is looked up rather than remembered.

For commercial plans, the obligation usually comes from state law. Most states have prompt-pay statutes that require an insurer to pay a clean claim within a set time and to add interest, a penalty, or both when it does not — enforced by the state department of insurance. The periods and rates vary from state to state, and they do not always apply at all: a self-funded employer plan is generally governed by federal law rather than state insurance law, so a state prompt-pay rule may not reach it. For Medicaid, timely-payment rules are set federally and by each state program. The one safe generalization is that there is no safe generalization about the figure.

Interest usually arrives on the same electronic remittance advice — the 835 — as the claims it relates to, but it is not reported inside any of them. It sits in the provider-level summary at the end of the file, among the amounts that act on the account as a whole rather than on a single claim. That level, and how the 835 is built around it, is the subject of How to Read an 835; here the point is only which level interest lives on, and what that does to the deposit.

In the provider-level adjustment segment — PLB — interest is carried under its own adjustment reason code, L6, distinct from the codes used for offsets and recoupments. Because it is a credit to the provider reported at that level, it raises the total paid above the sum of the individual claim payments. This is the mirror image of a recoupment: a recoupment is a provider-level amount that makes the deposit smaller than the claims it accompanies, and interest is a provider-level amount that makes it larger. In both cases the claims themselves look untouched and the difference lives in the summary.

The practical consequence is that a deposit larger than its claims is not automatically an error to chase. Payment Reconciliation is where that gap first shows up, because it is the step that compares the remittance to the money received — and interest is one honest reason the two would not match. A team that does not expect it will treat the overage as a mystery; a team that does will read the provider-level summary and find it named.

The rule follows from what interest is. Post each claim at exactly what the payer adjudicated — no more, because the payer did not allow more — and post the interest as a separate amount, recorded as interest or other income rather than as a payment on any claim. The claim's record stays a clean statement of the adjudication; the interest becomes its own line, tied to the payer and the period rather than to a service.

Posting interest correctly also keeps it out of accounts receivable logic it does not belong to. Interest is not a contractual adjustment and not a balance a patient could ever owe; it is income the practice earned by being paid late, and it closes nothing on the claim it accompanied. Left applied to a claim, it can even close a balance that was genuinely short, hiding a real underpayment behind money that had nothing to do with the service.

Because it arrives as extra money on the remittance, interest can be mistaken for the two things that also arrive as unexpected money — an underpayment or an overpayment. It is neither, and the difference is precise. A variance is the claim paid wrong — short of the contracted rate, or beyond what was owed. Interest is the claim paid right, but late, with a separate amount the payer owes for the delay. The claim's adjudication was correct; only its timing was not.

The remittance keeps them apart on purpose. Interest carries its own provider-level reason code, and an amount a payer recovers because it overpaid carries a different one; the standard treats the two as separate concepts and does not permit them to be combined into a single provider-level adjustment. So the same file that pays interest for being late can, in the very next line, recover an overpayment it made earlier — and the codes are what tell a poster that one is money owed to the practice and the other is money leaving it.