CO 135 denial code

Claim adjustment reason code 135. Often reported as CO 135.

Interim bill cannot be processed

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 135 means

The payer will not process an interim bill for this stay and expects a different bill type, often a final bill.

Interim bills cover part of a longer stay and are sent before discharge. With this code the payer is saying it does not accept or process interim bills for this claim, so nothing was paid on it.

The usual fix is to wait until the stay ends and send one complete bill, or to follow the payer's rules on when interim billing is allowed. Check the bill type code on the claim.

Group codes seen with 135

On a remittance, 135 comes after a group code. These are the ones it is most often reported with:

• CO 135 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The payer does not accept interim billing for this type of stay or provider.
• An interim bill type was sent when the payer expected an admit-through-discharge bill.
• The interim bill did not meet the payer's minimum length of stay for split billing.

What to do next

1. Check the bill type and frequency code on the claim against the payer's interim billing rules.
2. Hold the account and send a complete admit-through-discharge bill once the patient is discharged.
3. If interim billing is allowed for this stay, resubmit with the correct bill type and dates.

Related codes

• 16 (reason code) Missing information or billing error
• 190 (reason code) Included in qualified SNF stay payment