DALP transaction fee: per-transfer fee deduction

Per-transaction fee deducted from transfer amounts on every mint, burn, or transfer. Uses supportsRewriting to reduce the amount in-flight before compliance checks and recipient receipt.

Purpose: Transaction Fee deducts a per-transaction fee from every mint, burn, or transfer by rewriting the transfer amount in-flight. The recipient receives amount - fee; the fee goes to a configured recipient.

Doc type: Reference
What you'll find here: Business impact, risks, controls, failure modes, auditability, dependencies, and ordering notes
Related:

Interface (capabilities)

This feature exposes the following capabilities. It is a rewriting feature — it modifies the transfer amount in-flight, so the recipient receives the post-fee amount.

Capability	Who can call	Inputs	On-chain effect	Emits	Notes
Deduct fee on operation	Automatic (hook)	Triggered on mint, burn, transfer	Rewrites amount; routes fee to recipient	`TransactionFeeCollected`	`supportsRewriting = true`
Set fee rates	`GOVERNANCE_ROLE`	Rates per operation type (mint, burn, transfer in bps)	Updates fee rate configuration	`FeeRatesUpdated`	Blocked after freeze
Set fee recipient	`GOVERNANCE_ROLE`	Recipient address	Redirects future fee collection	`FeeRecipientUpdated`	Effective immediately
Freeze fee rates	`GOVERNANCE_ROLE`	None	Permanently locks all rates	`FeeRatesFrozen`	Irreversible

Business impact

Holders: Net-based fee — holders receive less than the face amount of a transfer. Senders initiate transfers for gross amount; recipients receive net.
Issuer / recipient: Fee collected in the token itself to configured feeRecipient.
Economics: Deducted on every operation (mint, burn, transfer). Fee rates can differ per operation type.

Risks & abuse cases

Compliance module ordering risk: Because supportsRewriting = true, the amount is rewritten before compliance modules run their checks. A compliance module checking minimum transfer amounts will see the post-fee (reduced) amount. Coordinate fee rates and compliance thresholds.
Rate freeze timing: Leaving freezeFeeRates() uncalled allows GOVERNANCE_ROLE to raise rates after deployment. Call at launch.
High-frequency fee accumulation: Platforms with high transaction volume should monitor fee recipient balance; unexpected recipient addresses can drain value.

Controls & guardrails

Role	Actions	Recommended guardrail
`GOVERNANCE_ROLE`	`setFeeRates()` — set fee rates per operation	Call `freezeFeeRates()` after launch
`GOVERNANCE_ROLE`	`setFeeRecipient()` — set fee destination	Multi-sig; audit all changes
`GOVERNANCE_ROLE`	`freezeFeeRates()` — lock rates permanently	Call at launch

Failure modes & edge cases

Zero-amount transfer after fee: If fee equals the full transfer amount, the recipient receives zero tokens and the fee recipient receives the full amount. No revert — check minimum transfer amounts in compliance modules.
Fee on minting: Minting to a holder results in holder receiving amount - mint_fee. If mint semantics require exact amounts, account for the fee in the mint call.

Auditability & operational signals

TransactionFeeCollected(from, to, amount, fee, recipient) — emitted per transaction. Use for reconciliation and monitoring.
FeeRatesUpdated(sender, mintRate, burnRate, transferRate) — emitted on rate changes.
FeeRatesFrozen(sender) — emitted once on freeze.

Dependencies

No external ERC-20 required — fee paid in the token itself.
supportsRewriting = true — interacts with the amount-rewriting pipeline. Must run before analytics features.

Compatibility & ordering notes

Must run before: Historical Balances, Voting Power (analytics hooks must see post-fee amounts).
Compliance module interaction: Compliance checks receive the post-rewrite amount. If any module enforces minimum amounts, ensure thresholds account for maximum fee rates.
Compatible with AUM Fee (both collect in-token; order doesn't matter between them, but both before analytics).
Compatible with External Transaction Fee (two separate fee mechanisms; External runs after).

Change impact

Enable after launch: Only applies to transactions from activation point forward.
Disable: No retroactive effect. In-flight transactions complete at old rate.
Rate change before freeze: Effective immediately on next transaction.
Recipient change: Effective immediately for all future collections.

Transaction Fee