How is the OneOncology platform interest taxed?

That depends on the vehicle physicians hold their retained interest through. Partnership-taxed vehicles allocate income annually on K-1s; corporate stock waits for dividends or a sale. Platform events, like the put and call arrangements publicized in the 2023 transaction, are where the concentrated tax outcomes live for holders.

I am a partner in a OneOncology-affiliated practice. What does my annual tax life look like?

The standard practice-partner system: K-1 allocations from your practice, self-employment tax as an active physician partner, quarterly estimates, self-employed benefits, and basis tracking, plus whatever the platform stake adds. The network affiliation itself does not convert practice partners into employees.

Can I owe tax on the platform stake in a year it pays me nothing?

If the stake is held through a partnership-taxed vehicle, yes: allocations are taxable whether or not cash follows. Whether holders receive tax distributions to cover those allocations is set by the vehicle's documents, which is one of the first things worth checking about any retained interest.

What should an oncologist review when a platform acquires their practice?

The allocation of sale proceeds and its tax character, the structure and classification of any rollover or retained interest, the waterfall ahead of physician equity, expected tax distributions, employment terms after closing, and the state filing consequences. After-tax comparisons frequently reorder the attractiveness of competing bids.

K-1 Employer Guide

OneOncology and the Two-K-1 Oncologist

A practice partnership below, a platform stake above, and a liquidity clock ticking on someone else's schedule. Each layer has its own tax rules.

A guide by Taxstra Tax & Accounting · CPA-led tax strategy for business owners

Your Guide

01The Two Layers 02The Practice Layer 03The Platform Layer and Liquidity Events 04Frequently Asked Questions

K-1 & Partnership Taxes>OneOncology

Written by Bryan Martin, CPA, Managing Partner and Founder of Taxstra. Last updated August 20, 2026.

Quick answer

OneOncology-affiliated physicians commonly face two tax layers: their own practice, which can remain a partnership issuing K-1s, and the minority platform interest that practices, physicians, and management retained when TPG and AmerisourceBergen acquired OneOncology in 2023. Each layer's taxation follows its entity classification, and platform liquidity events concentrate the stakes.

When TPG and AmerisourceBergen acquired OneOncology in 2023 at a $2.1 billion valuation, public releases noted that the affiliated practices, physicians, and management retained a minority interest in the company. That single sentence describes the tax structure many OneOncology physicians now live in: a practice below, a platform stake above.

Structures vary by practice, deal vintage, and cohort, and your documents govern. This page maps the two layers and the tax rules each one runs on.

The Two Layers

Same physician, two unrelated pass-through relationships.

Layer	What it is	Typical tax character
Practice	Your ownership in the local practice entity	Active partner income: SE tax, estimates, partner deductions
Platform	Retained or rollover interest in the OneOncology enterprise	Investment-type income; concentrated gains at liquidity events

Never net the layers in your head

The practice layer and the platform layer have different income character, different state footprints, different basis schedules, and different risk. Physicians who mentally merge them into one number routinely misplan estimates in years when the layers move in opposite directions.

The Practice Layer

Standard partner taxation, unchanged by the logo on the building.

Where the affiliated practice remains a physician-owned partnership, partners keep the complete partner tax system: self-employment tax on allocations, quarterly estimates, self-employed benefits, and partner deductions. Where a transaction converted physicians to employment, the practice layer collapses into a W-2 and the platform layer carries all the pass-through complexity.

The Platform Layer and Liquidity Events

Quiet years, then a letter with a deadline.

Publicized arrangements in the 2023 transaction gave the buyers a structured pathway toward full ownership in later years. For physician holders, the planning implication is that the platform's liquidity timing is largely outside your control, which makes advance preparation the whole game: know your basis, know your vehicle's classification, know whether tax distributions cover annual allocations, and treat any exercise year as a projection year with estimates set early. The exit mechanics run on the same rules as our practice sale guide.

Taxstra CPA Tip

If your platform interest is partnership-taxed, request the basis schedule now, not in the liquidity year. Reconstructing basis across a practice sale, a rollover, and several K-1 years under a transaction deadline is expensive; maintaining it annually is nearly free.

Two K-1s and a Platform Event on the Horizon?

Multi-layer oncology structures reward a CPA who has mapped them before the liquidity letter arrives. Taxstra can build that map. The initial consultation is free.

Frequently Asked Questions

Frequently yes, from one or both of two sources: their own practice, if it remains a physician-owned partnership inside the network, and the platform stake, since OneOncology's affiliated practices, physicians, and management retained a minority interest in the company through the TPG and AmerisourceBergen transaction. The forms depend on each entity's classification, and your documents govern.

Public reporting describes arrangements giving AmerisourceBergen a pathway to full ownership several years after the 2023 closing. For physician holders, a future exercise of such rights would be a liquidity event: potentially large gain in a single year, with the timing controlled by parties other than you. That is precisely the kind of event to plan estimates and charitable or retirement offsets around in advance.

Plan Both Layers Before the Next Transaction

Practice allocations, platform stakes, and exit events all interact on one return: yours. Book a free initial consultation with a Taxstra CPA.

Next Steps

Filing it yourself is fine. Optimizing it is where the money is.

Getting the form right keeps you out of trouble. The strategies below are what actually lower the bill.

Want a CPA to run the numbers for you?

Free 30-minute call with a Taxstra CPA. No pressure, just the math for your situation.

Authoritative Sources

Citations reflect U.S. federal tax law as of the article's last reviewed date.

Related K-1 Employer & Partnership Guides

US Oncology Network

The MSO alternative in community oncology.

Radiology Partners

The rollover equity model in radiology.

Partnership Tax Basis

Tracking both interests correctly.

Ownership Models

All five structures, compared.