Bitcoin was the first cryptocurrency, and it still causes the most confusion come tax time. Unlike Ethereum's account model, Bitcoin uses a fundamentally different system called UTXO — and understanding it is key to accurate tax reporting.
Bitcoin's Unique Architecture: UTXO
UTXO stands for Unspent Transaction Output. Instead of an account balance like a bank, every satoshi you receive is an unspent output that can be used as an input in a future transaction.
Here's why this matters for taxes: when you spend BTC, you're typically consuming multiple UTXOsand creating new ones. Each UTXO has its own cost basis — and the IRS wants to know exactly which ones you spent.
🔑 Key Concept: Specific Lot Identification
With UTXOs, you can theoretically identify exactly which Bitcoin you spent — and when. This gives you control over which tax lots you sell, potentially minimizing taxes.
Bitcoin Address Formats
Bitcoin has four address formats, each with different prefixes:
| Format | Prefix | Example | Notes |
|---|---|---|---|
| P2PKH | 1... | 1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2 | Legacy |
| P2SH | 3... | 3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy | Wrapped SegWit |
| bech32 | bc1q... | bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq | Native SegWit |
| Taproot | bc1p... | bc1p0plr3ed22ra3z98ktz6t4k9z6j2kqrz9z7lq | Latest (2021) |
All formats are taxable the same way. The difference is mainly in transaction fees and privacy. Your tax software must read all four formats accurately.
Taxable Events for Bitcoin
- Selling BTC for fiat — Capital gain or loss
- Trading BTC for other crypto — Two events (sell BTC, buy other token)
- Spending BTC on goods/services — Disposal at fair market value
- Mining rewards — Ordinary income at FMV when received
- Lightning Network rewards — Ordinary income
- Receiving from forks — Ordinary income (e.g., Bitcoin Cash)
Non-Taxable Events
- Buying BTC with fiat — Establishing cost basis only
- Transferring between your own wallets — No disposal
- Holding BTC — Unrealized gains aren't taxed
- Gifting BTC — Different rules (gift tax may apply)
Bitcoin Forks: The Special Case
When Bitcoin Cash (BCH), Bitcoin SV (BSV), or Bitcoin Gold (BTG) forked from Bitcoin, you received new tokens based on your BTC holdings. The IRS treats this as:
- Ordinary income at fair market value on the fork date
- New cost basis in the forked tokens = that FMV
- Future gains calculated from that basis
⚠️ Important: Fork Documentation
If you received Bitcoin Cash at the 2017 fork, you must document the FMV on August 1, 2017. This can be challenging — CoinGecko historical data helps here.
Bitcoin Mining Taxes
Mining Bitcoin creates two tax events:
- Receipt of rewards — Ordinary income at FMV on receipt date
- Sale or disposition — Capital gain/loss on the difference
Additionally, mining expenses (electricity, hardware, pool fees) are typically deductible as business expenses if you're actively mining.
Lightning Network
The Lightning Network enables instant BTC transactions. Here's the tax treatment:
- Opening a channel — Generally not taxable (moving your own BTC)
- Routing payments — Income (fees earned)
- Closing a channel — Capital gain/loss calculation
Cost Basis Methods for Bitcoin
With UTXOs, you have options. The most common methods:
FIFO (Default)
Sell oldest BTC first
LIFO
Sell newest BTC first
HIFO
Sell highest cost basis first
Specific Lot
Choose exact UTXOs to spend
💡 Pro Tip: HIFO Saves Taxes
If you bought BTC at different times, selling your highest-cost BTC first minimizes gains. With UTXOs, this is explicitly trackable.
How Arthur Labs Handles Bitcoin
- Full UTXO tracking across all address formats
- Historical price at exact transaction time (not daily close)
- Fork event detection and FMV calculation
- Mining reward classification as income
- Lightning channel open/close tracking
Don't Let Bitcoin Taxes Surprise You
We scan your BTC addresses and handle the UTXO complexity automatically.
Scan Your Wallet →Disclaimer: This article is for educational purposes only. Bitcoin tax treatment can be complex — consult a qualified tax professional.