How do I fix OHIP error code S1?

Check the listing. If the Schedule gives a separate bilateral fee or says the fee covers both sides, bill according to that listing. Otherwise, the payment follows the Surgical Preamble and there is nothing to fix. If you believe the reduction was applied wrongly, for example the procedures were not bilateral, send a Remittance Advice Inquiry (RAI) through eSubmit, or on form 0918-84, within 7 months of the RA date.

When shouldn't I resubmit a S1 claim?

The payment matches the unilateral fee plus 85%. The claim is already on your Remittance Advice. Use an RAI, not a new claim.

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Error code

S1 — Bilateral surgery (one stage) paid at unilateral fee + 85%

Q: What does OHIP error code S1 mean?

S1 means a one-stage bilateral procedure was paid at the unilateral fee plus 85% for the second side. This is the standard bilateral rule.

Bilateral procedure reduced

A one-stage bilateral procedure was paid at the unilateral fee plus 85% for the second side.

What to do: Check the listing for a separate bilateral fee; otherwise the payment follows the standard rule and nothing needs fixing.

Code: S1
Description: Bilateral surgery (one stage) paid at unilateral fee + 85%

Explanation

Updated October 26, 2026

S1 means a one-stage bilateral procedure was paid at the unilateral fee plus 85% for the second side. This is the standard bilateral rule.

What it means

Code S1 means OHIP paid a bilateral procedure done in one stage at the unilateral fee plus 85% of it for the second side.

Listed surgical fees are for one side only unless the Schedule says otherwise (SP4, paragraph 9). The Surgical Preamble says that when a surgeon does more than one procedure under the same anaesthetic, or within 14 days in the same hospital stay for the same condition, the major procedure is paid in full and the others at 85% of their listed fee. This applies to staged and bilateral procedures too (SP2, paragraph 3). This is usually an expected reduction, not an error.

Common causes

A bilateral procedure, billed as two sides, on the same day under the same anaesthetic (expected)

How to fix it

Check the listing. If the Schedule gives a separate bilateral fee or says the fee covers both sides, bill according to that listing.
Otherwise, the payment follows the Surgical Preamble and there is nothing to fix.
If you believe the reduction was applied wrongly, for example the procedures were not bilateral, send a Remittance Advice Inquiry (RAI) through eSubmit, or on form 0918-84, within 7 months of the RA date.

Don't resubmit if

The payment matches the unilateral fee plus 85%.
The claim is already on your Remittance Advice. Use an RAI, not a new claim.

How APEX handles it

APEX reads your error reports and remittance advice from MCEDT and lists claims rejected with this code in its Correction Centre for you to correct and resubmit. See how APEX works · Pricing

Related codes: S2, S3