> For the complete documentation index, see [llms.txt](https://www.aevo.xyz/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.aevo.xyz/docs/aevo-products/aevo-builder-codes/faq.md).

# FAQ

**Who can become a builder?** Any Aevo account holding at least the minimum USDC balance (currently 100 USDC). Registration is self-service and takes effect immediately.

**Can I choose my builder ID?** No. Aevo generates it (`builder_` followed by 16 hex characters). You choose the display name and can change it later.

**Can I change my fee account?** No. The account that registers the builder is its fee account for good, so use a dedicated account.

**Which markets are supported?** Perpetuals and options.

**How much can a builder charge?** Up to the maximum each user approved, and never above Aevo's protocol cap: **5 bps on perpetuals**, and **3 bps of index notional on options, never more than 5% of the premium**. Anything higher is rejected. Caps are also published at [`GET /builder-config`](/docs/api-reference/urls/public-api/getbuilderconfig.md).

**Can a builder charge different fees for different trades?** Yes. The fee rate is set per order, anywhere from zero up to the user's approved maximum.

**Do builders earn on maker and taker trades?** Yes. The builder fee applies whether the order is the maker or the taker.

**When are builder fees paid?** On every fill, in USDC, straight into the builder's fee account.

**Is the builder fee part of Aevo's trading fee?** No. It's charged separately and shown separately on every fill.

**What happens if a user revokes, or a builder is suspended?** New orders with that builder are rejected. Fills of orders already on the book still execute, with a builder fee of zero.

**Can a builder withdraw a user's funds?** No. A builder approval only authorizes a fee. Withdrawals and transfers always require the user's wallet signature.

**Where do builders see their earnings?** In **Settings → Builders → Builder Dashboard**, or through the [Reporting API](/docs/api-reference/builder-codes/reporting-api.md), including a CSV export of every attributed fill.

**Is there a testnet?** Yes, at [testnet.aevo.xyz](https://testnet.aevo.xyz). See the [testnet guide](/docs/api-reference/builder-codes/testnet-and-reconciliation.md).


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