Icrc Ledger

Handles ICRC-1 and ICRC-2 token operations on the Internet Computer: transfers, balance checks, and approve/transferFrom flows for ICP, ckBTC, and ckETH. The source walks you through the common landmines like hardcoding fees across ledgers, forgetting that mints and burns require zero fees, and the minting account gotcha where it can't call approve. Covers both Motoko and Rust with actual canister IDs and index canisters. Use this when you're moving tokens around or building allowance-based flows. Don't use it for ckBTC minting or BTC withdrawal, there's a separate skill for that.

skills.sh installs: 278
GitHub stars: 39
last updated: Aug 21, 2026

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Install

$ npx -y skills add dfinity/icskills --skill icrc-ledger --agent claude-code

Installs into .claude/skills of the current project.

Files

ICRC Ledger Standards

What This Is

ICRC-1 is the fungible token standard on Internet Computer, defining transfer, balance, and metadata interfaces. ICRC-2 extends it with approve/transferFrom (allowance) mechanics, enabling third-party spending like ERC-20 on Ethereum.

Prerequisites

For Motoko: mops with core = "2.3.1" in mops.toml
For Rust: ic-cdk = "0.19", candid = "0.10", icrc-ledger-types = "0.1" in Cargo.toml

Canister IDs

Token	Ledger Canister ID	Decimals
ICP	`ryjl3-tyaaa-aaaaa-aaaba-cai`	8
ckBTC	`mxzaz-hqaaa-aaaar-qaada-cai`	8
ckETH	`ss2fx-dyaaa-aaaar-qacoq-cai`	18

Index canisters (for transaction history):

ICP Index: qhbym-qaaaa-aaaaa-aaafq-cai
ckBTC Index: n5wcd-faaaa-aaaar-qaaea-cai
ckETH Index: s3zol-vqaaa-aaaar-qacpa-cai

All ICRC-1 ledgers expose icrc1_fee : () -> (nat) query to return the current transfer fee. Fees are denominated in the token's smallest unit (e8s for ICP where 1 ICP = 10⁸ e8s, satoshis for ckBTC, wei for ckETH). Each ledger sets its own fee, and fees can change at runtime.