> For the complete documentation index, see [llms.txt](https://docs.probly.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.probly.com/fees-and-settlement/fees.md).

# Fees

How trading fees work on Probly.

Probly charges a small **taker fee** on trades that match immediately against the order book.

* **Always paid in USDC** — never deducted from your shares. The number of shares you enter is exactly what you receive (or deliver)
* **Only takers pay** — limit orders that rest on the book (makers) are never charged. See [How Orders Match](/markets-and-trading/matching-logic.md) for how maker vs taker is decided
* **Shown separately** in the order panel before you confirm, then applied automatically at match time

## Fee Formula

```
takerFee = C × p × takerFeeRate × (p × (1 − p))^exponent
```

| Symbol           | Meaning                                      |
| ---------------- | -------------------------------------------- |
| **C**            | Number of shares traded                      |
| **p**            | Execution price (between 0.01 and 0.99 USDC) |
| **takerFeeRate** | Per-market fee rate                          |
| **exponent**     | Per-market curve exponent                    |

{% hint style="info" %}
**takerFeeRate** and **exponent** are set per market and published on the market page before you trade.
{% endhint %}

## **Fee Rates by Market Category**

`TakerFeeRate` is assigned based on the market's category. The Fee Type Code appears in the order breakdown before you confirm a trade. `MakerFeeRate` is currently set to 0.

<table data-search="false"><thead><tr><th>Category</th><th>Fee Type Code</th><th>Taker Fee Rate</th><th>Maker Fee Rate</th><th>Exponent</th></tr></thead><tbody><tr><td>General</td><td>PBLGEN</td><td>0.05</td><td>0.00</td><td>1×</td></tr><tr><td>Weather</td><td>PBLWTH</td><td>0.05</td><td>0.00</td><td>1×</td></tr><tr><td>Culture</td><td>PBLCUL</td><td>0.05</td><td>0.00</td><td>1×</td></tr><tr><td>Economics</td><td>PBLECO</td><td>0.05</td><td>0.00</td><td>1×</td></tr><tr><td>Mentions</td><td>PBLMEN</td><td>0.04</td><td>0.00</td><td>1×</td></tr><tr><td>Tech</td><td>PBLTEC</td><td>0.04</td><td>0.00</td><td>1×</td></tr><tr><td>Politics</td><td>PBLPOL</td><td>0.04</td><td>0.00</td><td>1×</td></tr><tr><td>Finance &#x26; Prices</td><td>PBLFIN</td><td>0.04</td><td>0.00</td><td>1×</td></tr><tr><td>Crypto</td><td>PBLCRY</td><td>0.07</td><td>0.00</td><td>1×</td></tr><tr><td>Sports</td><td>PBLSPO</td><td>0.05</td><td>0.00</td><td>1×</td></tr><tr><td>Others</td><td>PBLOTH</td><td>0.04</td><td>0.00</td><td>1×</td></tr></tbody></table>

The exponent scales the fee curve: at 1, the curve applies linearly with no additional adjustment. Future categories or promotional periods may use a different exponent.

## The Fee Curve

The factor *p × (1 − p)* shapes the curve — it peaks at *p = 0.50* and tapers toward both extremes:

<figure><picture><source srcset="/files/vCqvpn9DNIT2bnpLpPBj" media="(prefers-color-scheme: dark)"><img src="https://2587188963-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FZpNZvaCzAbpqVCg9WNwK%2Fuploads%2Fgit-blob-687bd0151aea40059ad1c7fbfd5623b7c734b2ea%2Fsettlement_fees_1.svg?alt=media" alt=""></picture><figcaption></figcaption></figure>

In practice:

* **Fees peak at 50% probability** — where uncertainty is highest
* **Fees shrink toward both ends** — a heavy favorite at 95¢ costs much less to trade than a coin-flip at 50¢
* **Symmetric around 50¢** — a trade at 30¢ costs the same dollar fee as the same-size trade at 70¢
* **Very small trades near the extremes may incur no fee at all** (see [Fee Precision](#fee-precision))

## How You're Charged

Every order panel breaks the trade into the same fields:

| Field                  | What it means                                                     |
| ---------------------- | ----------------------------------------------------------------- |
| **Shares**             | Exactly what you'll receive (buy) or deliver (sell)               |
| **Order Value**        | Shares × Price                                                    |
| **Est. Fee**           | The taker fee estimate in USDC                                    |
| **Total** (buy)        | Order Value + Est. Fee — the exact amount that leaves your wallet |
| **Net Receive** (sell) | Order Value − Est. Fee — the USDC credited to your account        |

For the same size and price, the USDC fee is identical in either direction.

## Estimate vs Actual

The **Est. Fee** is calculated at the **highest possible rate** (fully taker at *p = 0.50*). The **actual fee** is set at match time from the fill price — so the final amount is **at most** the estimate, usually less.

> Hover the **ⓘ** icon next to **Total** (buy) or **Net Receive** (sell) to see the breakdown.

## Worked Example

Buying **5 shares** at a limit price of 80¢:

| Field       | Value                                                                    |
| ----------- | ------------------------------------------------------------------------ |
| Shares      | 5                                                                        |
| Order Value | 5 × $0.80 = $4.00                                                        |
| Est. Fee    | ≈ $0.03                                                                  |
| **Total**   | **$4.03**                                                                |
| To Win      | $5.00 if YES wins, $0 if it loses *(total payout — includes your stake)* |

You pay **$4.03** and receive exactly **5 shares**.

### Curve Factor at Key Prices

| Price (p) | Curve factor (p × (1 − p)) | Relative fee   |
| --------- | -------------------------- | -------------- |
| 50¢       | 0.2500                     | Highest        |
| 40¢ / 60¢ | 0.2400                     | Slightly lower |
| 30¢ / 70¢ | 0.2100                     | Moderate       |
| 10¢ / 90¢ | 0.0900                     | Low            |
| 5¢ / 95¢  | 0.0475                     | Very low       |

## Fee Precision

* Fees are rounded to 4 decimal places in USDC
* Smallest charged: **0.0001 USDC**
* Anything below that rounds to zero — very small trades near the price extremes may incur no fee at all

## Where to Find Your Fee

* **Before** a trade — estimated fee and final total appear in the order panel

## Related

* [How Orders Match](/markets-and-trading/matching-logic.md) — how maker / taker is determined
* [Market Orders](/markets-and-trading/market-orders.md) — execute immediately at the best price
* [Limit Orders](/markets-and-trading/limit-orders.md) — rest on the book at your chosen price
* [Deposits & Withdrawals](/get-started/deposits-and-withdrawals.md) — free deposits, 1 - 2 USDC withdrawal fee
* [Referrals](/fees-and-settlement/referrals.md) — earn a share of fees from users you invite


---

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