Every time you sell a stock, crypto token, or piece of property, the IRS asks one deceptively simple question: what did you pay for it? The answer — your cost basis — determines your capital gain or loss, which determines your tax bill. But when you've bought the same asset at different prices over time, which purchase price do you use?
This question has shaped American tax law for over a century. From the Revenue Act of 1918 to the crypto reporting mandates of 2024, the rules governing cost basis methods have evolved through legislation, regulation, and technological change. The three methods that emerged — FIFO, LIFO, and Specific Identification — aren't just accounting conventions. They're strategic levers that can shift thousands of dollars between your pocket and the Treasury. This is the full story of how they came to be.
Revenue Act of 1918 — The Foundation
The first modern income tax legislation allowed taxpayers to identify specific lots of securities when calculating gains and losses. This was the birth of specific identification — the idea that you could choose which shares you sold, not just assume you sold the earliest ones purchased.
FIFO Becomes the Default Assumption
As stock market participation grew, the IRS adopted First-In, First-Out as the default method when taxpayers couldn't identify specific lots. If you couldn't prove which shares you sold, the government assumed you sold the oldest ones first — a rule that persists to this day.
Internal Revenue Code Formalized
Congress codified the tax code into the Internal Revenue Code of 1939, formally recognizing both FIFO and specific identification as acceptable cost basis methods. LIFO gained indirect recognition through inventory accounting provisions in Section 22(d), giving businesses their first clear path to using it.
IRC §1012 — The Statutory Anchor
The Internal Revenue Code of 1954 established Section 1012, which remains the primary statute governing cost basis today. It states that basis is generally the cost of property — but Treasury regulations would spend decades clarifying what "cost" means when you own hundreds of identical shares bought at different prices.
Treasury Regulation §1.1012-1(c) — The Lot ID Rule
The Treasury issued Regulation §1.1012-1(c), establishing the three acceptable methods for identifying which shares were sold: specific identification, FIFO, and average basis for regulated investment companies. This regulation — still in force — is the backbone of cost basis methodology for individual investors.
Tax Reform Act of 1986 — LIFO Tightened
The landmark Tax Reform Act of 1986 overhauled depreciation rules and indirectly affected LIFO. While LIFO remained available for inventory accounting under §472, the act's replacement of ACRS with MACRS introduced a statutory depreciation method that functions like FIFO for capital recovery — taxpayers must use prescribed percentage tables rather than choosing their own recovery order.
FIFO Dominates Individual Investing
By the early 1990s, FIFO had become the de facto standard for individual investors. Most brokerages defaulted to FIFO for reporting capital gains, and few retail investors knew they could specify lots. For the average American with a brokerage account, cost basis was whatever the 1099-B said it was.
EESA Mandates Broker Reporting
The Emergency Economic Stabilization Act of 2008 included a quiet provision that would transform cost basis tracking: it mandated that brokers report cost basis to the IRS on Form 1099-B, starting with equities in 2011, mutual funds in 2012, and other securities in 2013. For the first time, the IRS could match reported gains against broker data.
The Story Isn't Over
Cost basis rules are evolving faster than ever — especially for digital assets. Get Elena's weekly brief on the moves that matter.
You're In
Check your inbox for a welcome email from Elena.
Broker Cost Basis Reporting Begins
Starting January 1, 2011, brokers were required to report cost basis for equities purchased on or after that date. This created the "covered" vs. "non-covered" distinction that still confuses investors today. Pre-2011 purchases remained "non-covered" — the broker didn't report basis, and the taxpayer was on their own.
Mutual Funds and DRIPs Enter the System
The reporting mandate expanded to include mutual fund shares and dividend reinvestment plans. Average basis became the standard default for fund shares — a simplified method that blends all purchase prices into a single per-share cost. For investors in index funds with monthly contributions, this was a significant simplification.
IRS Rules: Virtual Currency Is Property
IRS Notice 2014-21 declared that virtual currencies like Bitcoin are treated as property for tax purposes — not currency. This meant every crypto transaction triggered capital gains or losses, and cost basis rules that had been designed for stocks now applied to an entirely new asset class with thousands of micro-transactions.
Form 8949 Becomes the Filing Battleground
By 2019, millions of Americans were filing Form 8949 to report securities sales, separated into covered and non-covered lots. The form became a maze of codes and adjustments. Taxpayers using dollar-cost averaging or automated investing often held dozens of lots in a single stock — and choosing the wrong method at sale could mean hundreds in unnecessary taxes.
Infrastructure Law Targets Crypto Reporting
The Infrastructure Investment and Jobs Act expanded the definition of "broker" to include crypto exchanges and DeFi protocols, requiring them to report digital asset transactions to the IRS. The provision sent shockwaves through the crypto industry and signaled that cost basis tracking for digital assets would soon face the same rigor as traditional securities.
IRS Proposes Digital Asset Broker Rules
The IRS released proposed regulations defining who qualifies as a digital asset broker and what they must report. The rules would require exchanges to track and report cost basis for every transaction — effectively forcing the crypto industry to build the same infrastructure brokers had spent a decade constructing for equities.
Rev. Proc. 2024-28 — The Crypto Transition
The IRS issued Revenue Procedure 2024-28, providing transition rules for digital asset cost basis methods. Taxpayers were given until January 1, 2025, to switch from universal wallet methods to per-wallet or per-account tracking — a change that affects every crypto holder who previously pooled their basis across multiple wallets.
Form 1099-DA and the New Reporting Era
The IRS began requiring digital asset brokers to report on Form 1099-DA — a new form purpose-built for crypto transactions. For the first time, crypto investors receive the same cost basis reporting that stock investors have had since 2011. The form includes fields for acquisition date, cost basis, and proceeds — making FIFO the default unless the taxpayer affirmatively selects another method.
AI, Automation, and the Future of Lot Selection
Tax software and brokerage platforms are beginning to offer algorithmic lot selection — systems that automatically choose the optimal shares to sell for tax purposes, often using a "tax lot optimizer" that blends FIFO, LIFO, and specific identification to minimize the current year's tax bill. The IRS has not yet issued formal guidance on whether these automated selections satisfy the "adequate identification" requirement of §1.1012-1(c).
Where We're Headed
The 106-year arc of cost basis rules tells a clear story: what began as a simple choice between FIFO and specific identification has become a complex web of reporting requirements, asset-class-specific rules, and technology-driven compliance mandates. The trajectory points toward total transparency — the IRS wants to know the cost basis of every asset you sell, reported by the institution that facilitated the transaction.
For investors, the strategic implications are significant. The days of casually selling shares without considering cost basis are ending. Whether you hold equities, mutual funds, or digital assets, the method you choose — or fail to choose — directly impacts your tax bill. FIFO remains the default, but it's rarely the optimal method. Specific identification, when properly documented, gives you the most control. And for business inventory, LIFO still offers legitimate deferral benefits under §472.
Looking ahead, three forces will reshape cost basis strategy: blockchain-native tracking that could make specific identification automatic and irrefutable, AI-powered tax optimization that selects lots in real time, and continued regulatory expansion into every corner of the digital economy. The investors who understand these rules — and plan accordingly — will keep thousands more of what they earn. Those who don't will continue subsidizing those who do.