HARBURGER

Harberger tax NFT. You buy the burger, set your own price, and pay continuous tax on that price. Anyone can force-buy it from you at the price you set. If you can't cover your taxes, anyone can take it for free. Deposited funds can optionally earn yield through Aave or Compound.

Setup

npm install
cd frontend && npm install && cd ..

Build & Test

npx hardhat compile
npx hardhat test

Configuration

Copy .env.example to .env and fill in your values:

cp .env.example .env

Key settings:

• PRIVATE_KEY — deployer wallet private key (without 0x)
• SEPOLIA_URL / MAINNET_URL — RPC endpoint (Alchemy, Infura, etc.)
• TAX_RECEIVER — address that receives tax payments
• ANNUAL_TAX_PERCENT — annual tax as a percentage of declared price (default: 10)
• INITIAL_PRICE — starting price in Wei (default: 0.001 ETH)

The deploy script converts ANNUAL_TAX_PERCENT to a per-second rate scaled by RATE_PRECISION (1e18). You can override this by setting TAX_RATE directly.

DeFi strategy addresses (AAVE_POOL_ADDRESSES_PROVIDER, WETH_ADDRESS, AWETH_ADDRESS, COMPOUND_COMET) are optional. Leave as zero addresses to skip strategy deployment.

Deploy

npm run deploy:sepolia    # testnet
npm run deploy:mainnet    # production

Deployment addresses are saved to deployments-<network>.json.

Verify

npx hardhat verify --network <network> \
  HARBURGER_ADDRESS \
  "NFT_NAME" "NFT_SYMBOL" \
  TAX_RATE TAX_RECEIVER INITIAL_PRICE TAXVAULT_ADDRESS

Constructor values are in the deployment JSON file.

Frontend

cd frontend
cp .env.example .env
# Set VITE_CONTRACT_ADDRESS to your deployed Harburger address
npm run dev

How It Works

1. The deployer mints the NFT and sets an initial price
2. The owner pays continuous taxes (per-second, proportional to their declared price)
3. Anyone can deposit ETH, then force-buy the NFT at the current price
4. The owner can earmark the NFT for a specific address with an optional deposit
5. If the owner runs out of funds, the NFT can be claimed for free
6. Deposited funds can optionally be routed through a TaxVault into yield strategies (Aave V3, Compound V3)

Tax Receiver

TAX_RECEIVER is set as a plain address at deploy time. If you use an ENS name, resolve it to an address first. To change the tax receiver after deployment, the contract owner calls updateTaxReceiver(newAddress).

Commands

Command	Description
npm run compile	Compile contracts
npm run test	Run tests
npm run node	Start local node
npm run deploy:localhost	Deploy locally
npm run deploy:sepolia	Deploy to Sepolia
npm run deploy:mainnet	Deploy to mainnet

Project Structure

contracts/
  Harburger.sol              Main Harberger tax NFT contract
  TaxVault.sol               Multi-strategy yield vault for tax deposits
  ITaxVault.sol              TaxVault interface
  IYieldStrategy.sol         Yield strategy interface
  strategies/
    AaveStrategy.sol         Aave V3 strategy
    CompoundStrategy.sol     Compound V3 strategy
test/
  Harburger.test.js
  TaxVault.test.js
scripts/
  deploy.js
frontend/
  src/
    App-harburger.jsx
    contractABI.js
    main.jsx
    index.css