HIFO Cost Basis: Specific-Lot Rules, Examples & Limits

HIFO (highest‑in, first‑out) is a lot‑identification rule that matches shares you sell to the previously purchased lots with the highest per‑share cost first. By assigning sales to higher‑cost lots, HIFO raises the cost basis for the shares sold and — all else equal — reduces the realized capital gain on that sale compared with many other methods Fidelity and Charles Schwab. This is a tax‑reporting convention: it changes which lot costs are used to compute gains or losses, not the cash you receive from the sale.

What HIFO Cost Basis Means

HIFO is a deterministic lot‑selection method applied when you hold multiple purchase lots of the same security. For a given sale, you match the shares sold to the lot(s) that have the highest per‑share purchase cost until the sale quantity is satisfied; those matched lot costs become the basis used to compute the taxable gain or loss. The basic concept — that cost basis equals what you paid plus transaction costs and that taxable gain equals sale proceeds minus that basis — is standard tax accounting practice Fidelity.

Scope and core points

• Cost basis should include purchase price and any fees or commissions that can be added to the lot cost; those increase the basis used to compute gain or loss Fidelity.
• The lot‑identification method (HIFO, FIFO, Specific ID, average cost, etc.) determines which lot costs are assigned to a sale and therefore affects the size and timing of reported gains or losses Charles Schwab.
• HIFO is relevant for taxable brokerage accounts where lots are tracked; tax‑advantaged pooled accounts may follow different rules or make lot selection irrelevant.

Define a couple of terms

• Lot: a group of shares bought in a single transaction with a single per‑share cost.
• Cost basis: the per‑share purchase cost (plus allowable fees) used to compute gain or loss when those shares are sold.

How It Works

Stepwise mechanics

1. Record each purchase lot with date, quantity, and per‑share cost (include commissions or fees when they can be added to that lot’s cost) — that recorded amount is the lot’s cost basis Fidelity.
2. When you place a sale for N shares, list the unsold lots for that security and their per‑share costs.
3. Under HIFO, select the lot(s) with the highest per‑share cost first; continue down the cost ranking until N shares are matched.
4. For each matched lot, compute realized gain or loss as (sale price − lot cost) × number of shares taken from that lot.
5. Sum the matched‑lot results to get the total realized gain or loss for the sale.

Compact formula - For matched lot i: realized_i = (P_sell − C_i) × Q_i - Total realized = Σ realized_i for all matched lots Where P_sell = sale price per share; C_i = cost per share of lot i; Q_i = shares matched from lot i.

Practical broker and recordkeeping notes

• Brokers commonly let you select a lot‑identification method or use a default if you do not specify one; that selection affects what gets reported to you and to tax authorities Charles Schwab.
• Accurate HIFO accounting requires complete lot history. Many brokers automate lot tracking and can apply HIFO when supported; doing it manually requires careful records to avoid reporting errors Fidelity.
• HIFO is a reporting rule: it changes tax reporting (which lots are considered sold) rather than cash proceeds or the economic return on the investment Fidelity.

Worked Example

Assumptions (hypothetical)

• Holdings in XYZ: three lots, 100 shares each.
• Lot A: 100 shares @ $50.00
• Lot B: 100 shares @ $70.00
• Lot C: 100 shares @ $40.00
• You sell 150 shares at $80.00 per share.
• Commissions and fees are treated as already included in the lot prices for simplicity.

Apply HIFO

1. Rank lots by per‑share cost: Lot B ($70), Lot A ($50), Lot C ($40).
2. Match 150 shares: 100 from Lot B and 50 from Lot A.
3. Compute realized gain per matched lot:

• Lot B: (80 − 70) × 100 = $10 × 100 = $1,000.
• Lot A: (80 − 50) × 50 = $30 × 50 = $1,500.

4. Total realized gain under HIFO = $2,500.

Compare to FIFO (for the same sale)

• FIFO would match Lot A (oldest) then Lot B partly:
• Lot A: (80 − 50) × 100 = $3,000.
• Lot B (50 shares): (80 − 70) × 50 = $500.
• Total FIFO realized gain = $3,500.

Interpretation of the numbers

• In this scenario HIFO reduced the immediate realized gain by $1,000 versus FIFO. The sale proceeds are identical; HIFO changed which lot costs are applied and therefore changed taxable gain timing and amount.
• Whether that tax timing is “better” depends on your objectives, holding periods, and future transactions; HIFO does not change the underlying cash flows from the investments Fidelity.

How to Interpret It

What HIFO does (and does not)

• Timing vs lifetime taxes: HIFO can lower taxable gains now by using higher lot costs, but it typically defers gains into the lower‑cost remaining lots; total lifetime tax depends on future sales and is not guaranteed to be lower overall Fidelity.
• Holding period interaction: Lot selection affects whether recognized gains are short‑term or long‑term because holding period is tied to the matched lot’s purchase date. Matching a high‑cost recent lot can convert what would have been a long‑term gain into a short‑term gain or vice versa, which changes the tax rate applied Charles Schwab.
• Administrative tradeoffs: Specific ID (you name the lots) gives precise control but requires documentation at sale; HIFO automates a high‑cost selection without per‑trade identification but still depends on accurate lot history and broker support Fidelity.

A simple decision framework (four questions)

1. Objective: Is minimizing current taxable gain your top priority, or do you prefer simple reporting and consistency?
2. Horizon: Do you expect to hold remaining lots long enough to qualify for long‑term rates?
3. Administration: Does your broker support HIFO or Specific ID, and are you willing to maintain documentation if you pick Specific ID? Charles Schwab
4. Documentation: Can you reconcile broker reports with your records if an audit or discrepancy arises? Fidelity

Two common misreads and why they fail in practice

• Misread 1: “HIFO eliminates taxes.” Reality: HIFO reallocates when gains are recognized; it can reduce taxes now but usually shifts tax to other lots to be realized later.
• Misread 2: “My broker will always use HIFO automatically.” Reality: broker defaults and the methods they support vary. Confirm the method your broker will apply if you do not make an election Charles Schwab.

Practical tip: If you use periodic investing (for example, automatic contributions or reinvested dividends), you will accumulate many lots. Those many lots are precisely why lot‑identification methods such as HIFO matter; see the glossary entry on Dollar Cost Averaging to understand how repeated purchases create multiple lots: Dollar Cost Averaging.