MBS items 51300 and 51303: the surgical assistant item numbers

Every assistant claim uses one item from Group T9 of the MBS. You never claim two of them for the same operation. Four terms come up again and again:

• Schedule fee. The fee the MBS sets for an item. Medicare pays a percentage of it.
• Marked operation. A surgical item whose MBS description ends in “(Assist.)”. Only marked operations pay an assistant, apart from the Caesarean, obstetric and cataract items below.
• Abated total. When you assist at more than one marked operation, Medicare reduces the fees under the Multiple Operation Rule: 100% for the largest, 50% for the next and 25% for each one after that. The sum is your abated total.
• Established fee. The figure some items take one fifth of. It is the operation’s schedule fee, or your abated total where there is more than one.

To pick the item, answer these in order:

1. Was there a Caesarean section? If nothing done with it carries “(Assist.)”, claim 51306. If you also assisted at a marked operation, claim 51309. See obstetric surgery.
2. Was it an interventional obstetric procedure (item 16606, 16609, 16612, 16615 or 16627)? Claim 51312.
3. Was it cataract and lens surgery? Claim 51315 or 51318 if the case meets their conditions. Otherwise there is no assistant item.
4. For any other operation, check it carries “(Assist.)”. If none of the operations do, there is no assistant item.
5. Work out your abated total over the marked operations you assisted at. At or below $668.25, claim 51300. Above $668.25, claim 51303.

Claim 51300 when you assist at a marked operation and the fee is $668.25 or less. If you assist at several marked operations, it is your abated total that must be $668.25 or less. The item pays a fixed $103.25, whatever the operation.

Common mistake. Claiming 51303 when the abated total is under $668.25. Medicare pays 51300 instead, or returns the claim. How the total is built.

Assistance at any operation mentioned in an item in Group T8 that includes “(Assist.)” for which the fee does not exceed $668.25, or at a series or combination of operations mentioned in an item in Group T8 that include “(Assist.)” for which the aggregate fee does not exceed $668.25.

MBS Online, Department of Health and Aged Care, item 51300, 1 July 2026

Claim 51303 when the marked operation’s fee, or your abated total, is over $668.25. There is no fixed fee. You take one fifth of the operation’s fee, or one fifth of your abated total.

The total that counts is yours, not the surgeon’s. Medicare runs the Multiple Operation Rule twice. Once over all the surgeon’s items, for the surgeon’s fee. Then again over only the marked items you assisted at, for yours. Your total is often lower, and can fall under $668.25 even when the surgeon’s is well over. The full method and four worked examples are in surgical assistants and the Multiple Operation Rule.

Common mistake. Taking one fifth of the surgeon’s total instead of your own abated total. Why the two totals differ.

Assistance at any operation mentioned in an item in Group T8 that includes “(Assist.)” for which the fee exceeds $668.25, or at a series or combination of operations mentioned in an item in Group T8 that include “(Assist.)” for which the aggregate fee exceeds $668.25. One fifth of the established fee for the operation or combination of operations.

MBS Online, Department of Health and Aged Care, item 51303, 1 July 2026

Obstetric surgery has its own assistant items. No obstetric item in Group T4 carries “(Assist.)”, so the Caesarean itself never counts towards 51300 or 51303. Which item you claim depends on two things: whether there was a Caesarean, and whether any operation done carries “(Assist.)”.

All three obstetric items, 51306, 51309 and 51312, are for admitted patients only. Medicare pays 75%.

Caesarean section alone: item 51306

Claim 51306 when you assist at a Caesarean and no marked operation is done with it. It is a fixed $149.25, and Medicare pays $111.95. The fee is the same whichever birth item the obstetrician claims. Procedures without “(Assist.)” done at the same time add nothing, and the item stays 51306 (TN.9.4).

For a privately insured patient, the fund schedule for 51306 comes to about $209.

Assistance at a birth involving Caesarean section (H).

MBS Online, Department of Health and Aged Care, item 51306, 1 July 2026

Caesarean with a marked operation: item 51309

Claim 51309 when you assist at a Caesarean and at one or more operations marked “(Assist.)” at the same time. Work out the fee in three steps:

1. Count the Caesarean as $755.05. This is the schedule fee for item 16520. Use it whichever birth item the obstetrician claims, including 16519 or 16522.
2. Apply the Multiple Operation Rule to everything, the Caesarean included. Rank the Caesarean and the marked operations by fee. The largest counts at 100%, the next at 50% and each one after that at 25%. Round the total up to the next 5 cents.
3. Divide the total by five. That is the 51309 fee.

The Caesarean is not always ranked first. In example 2 the hysterectomy has the larger fee, so the Caesarean counts at 50%.

51309 has no threshold. The total is always more than $755.05, so 51309 always pays more than the $149.25 of 51306.

Assistance at a series or combination of operations that include “(Assist.)” and assistance at a birth involving Caesarean section (H). One fifth of the established fee for the operation or combination of operations (the fee for item 16520 being the Schedule fee for the Caesarean section component in the calculation of the established fee).

MBS Online, Department of Health and Aged Care, item 51309, 1 July 2026

Obstetric surgery without a Caesarean

With no Caesarean, there are two routes to an assistant fee.

A marked operation: 51300 or 51303. Some Group T8 operations done around a birth carry “(Assist.)”, such as a peripartum hysterectomy after a vaginal birth. Use the $668.25 threshold, as in sections 03 and 04.

An interventional obstetric procedure: 51312. This covers items 16606, 16609, 16612, 16615 and 16627 only. The fee is one fifth of the procedure’s fee. Where there is more than one, it is one fifth of the abated total (TN.4.11, TN.9.1).

Other obstetric items do not pay an assistant. That includes 16618, 16621 and 16624, and the postnatal complication items.

Common mistakes at obstetric surgery.

• Claiming 51306 when a marked operation was also done. The claim is underpaid; the item is 51309.
• Claiming 51306 with 51300 or 51303 for the same birth. The combination has one item, 51309.
• Counting the Caesarean at the birth item’s own fee, such as 16522. It is always $755.05.
• Adding the marked operations to $755.05 at full fee instead of ranking them under the Multiple Operation Rule.
• Claiming 51312 for an obstetric item it does not list.

Both are for admitted patients only, paid at 75%.

MBS item 51315

Assistance at cataract and lens surgery (item 42698, 42701, 42702, 42704 or 42707) done with one of these associated procedures: 42551 to 42569, 42653, 42656, 42725, 42746, 42749, 42752, 42776 or 42779. Fixed fee $326.05, Medicare $244.55 (TN.9.1).

MBS item 51318

Assistance at cataract and lens surgery where either eye meets the item’s conditions. For the fellow eye: total loss of vision, or a past complication in it, such as vitreous loss, a ruptured posterior capsule, loss of nuclear material, intraocular haemorrhage or infection, cystoid macular oedema, corneal decompensation or retinal detachment. For the operated eye: one of the listed conditions, such as pseudoexfoliation, a subluxed lens or previous blunt trauma. Fixed fee $215.20, Medicare $161.40 (TN.9.1, TN.9.5).

Sometimes an operation is started and then stopped, for medical reasons or for reasons outside the surgeon’s control. The surgeon claims item 30001, at half the fee that would have applied. You claim the Group T9 item that would have applied, and Medicare pays half its fee. Write “assistance at abandoned surgery” on the claim (TN.8.5).

• The assistant item: 51300, 51303, 51306, 51309 or one of the obstetric or cataract items.
• The surgeon’s or obstetrician’s item numbers for the operations you assisted at. Medicare uses them to work out your fee.
• The surgeon’s name and provider number, the hospital and the date of service.
• A note on the claim where the rules ask for one: “assistance at abandoned surgery”; a return to theatre the same day as a separate procedure; two surgeons operating independently.
• For a known-gap claim, the patient’s informed financial consent on file before the list. Setting the fee and getting consent are covered in the surgical assistant billing guide.