Free mint NFTs aren’t actually free—you paid gas. That gas fee is your cost basis.

When you sell a free mint NFT, your taxable gain equals the sale price minus the gas you paid. Forgetting the gas basis means overpaying taxes on phantom gains.

How Gas Establishes Cost Basis

You minted a Goblintown NFT during the free mint. Gas cost: 0.08 ETH ($120 at the time).

Three months later, you sold it for 1 ETH ($1,500).

Without gas basis:

  • Cost basis: $0
  • Proceeds: $1,500
  • Taxable gain: $1,500

With gas basis:

  • Cost basis: $120 (gas fees)
  • Proceeds: $1,500
  • Taxable gain: $1,380

The $120 difference saves you $24-$44 in taxes depending on your bracket.

Multiply this across 50 free mints and you’re saving $1,200-$2,200.

Finding Your Gas Costs

Check Etherscan for the mint transaction. The total transaction fee is your cost basis.

Example Etherscan data:

  • Transaction Fee: 0.05 ETH
  • ETH Price at block time: $1,800
  • Cost basis: $90

Use the ETH price at the exact moment the transaction confirmed (Etherscan shows this). Don’t use today’s ETH price—use the historical price when you paid the gas.

Multiple Mints in One Transaction

Some contracts let you mint multiple NFTs in a single transaction.

You minted 3 Art Blocks pieces in one transaction. Gas: 0.15 ETH ($225 total).

Allocate gas equally across all three:

  • NFT #1 cost basis: $75
  • NFT #2 cost basis: $75
  • NFT #3 cost basis: $75

When you sell NFT #1 for $500, your taxable gain is $425 ($500 - $75), not $500.

Failed Mint Transactions

If your mint transaction failed and you paid gas but received nothing, that gas is a deductible loss in the year you paid it.

You tried to mint an Otherside land. Gas: 0.3 ETH ($450). Transaction failed due to network congestion. You got nothing.

That $450 is a capital loss. You can offset other gains or deduct up to $3,000 against ordinary income.

Allowlist vs. Public Mint

Whether you minted via allowlist (free) or public mint (paid fee + gas), the principle is the same: add all costs to your basis.

Allowlist free mint:

  • Mint price: $0
  • Gas: $80
  • Cost basis: $80

Public mint:

  • Mint price: 0.08 ETH ($120)
  • Gas: $25
  • Cost basis: $145

Always include gas in your cost basis calculation.

Tax Software Often Misses This

Most crypto tax software doesn’t automatically add gas fees to free mint cost basis. It sees a mint transaction with $0 price and assumes $0 basis.

You need to manually adjust each free mint entry to include gas fees.

Steps:

  1. Export your mint transactions from tax software
  2. Find the gas fee for each free mint on Etherscan
  3. Manually update cost basis to reflect gas paid
  4. Re-import or adjust entries

Tedious, but worth it if you minted dozens of free NFTs.

Proof for IRS

If the IRS questions why your “free mint” has a cost basis, show:

  1. Etherscan transaction showing gas paid
  2. Historical ETH price at the block timestamp
  3. Calculation converting gas ETH to USD

The blockchain is your receipt. Gas fees are real costs, and the IRS allows them as basis.

Action Step

Review all NFTs you minted this year. For each free mint, find the transaction hash and record the gas fee in USD.

Add those gas fees to your cost basis tracking spreadsheet or tax software.

If you already filed taxes and didn’t include gas basis on free mints, consider amending if the tax savings exceed $500. For smaller amounts, remember it for next year.

Free mints aren’t zero-basis assets—they cost you gas, and that gas reduces your taxes. Track it, claim it, save money.