Identify which custody rule governs
An owner selling part of a digital-asset holding needs to establish which units were disposed of. That choice determines both basis and holding period. For assets held in the custody of a broker, the current rules require an adequate identification to the broker by the date and time of the sale, disposition, or transfer. A later tax-software selection cannot simply replace an identification that the taxpayer never made when required.
The IRS provided temporary relief for certain 2025 transactions that allowed identification through taxpayer records. Its current guidance distinguishes transactions after December 31, 2025, for which the custodial broker must receive the qualifying identification or standing instruction. Treat a workflow tested during the relief year as something to reassess, not proof that the same private recordkeeping procedure works indefinitely. Unhosted wallets follow their own identification rules.
Compare two lots with explicit assumptions
Assume an individual holds two units of the same digital asset in one custodial brokerage account. One unit was purchased earlier for $24,000; the other was purchased later for $39,000. The owner sells one unit for $45,000 in 2026. Assume no fees, adjustments, other holdings, or special withholding facts. A valid identification of the later unit produces a simplified $6,000 gain. A disposition charged to the earlier unit produces a $21,000 gain.
The difference in currently recognized gain is $15,000. If both gains would be long term and an assumed 20% federal rate applies, the simplified difference in current federal tax is $3,000 before other taxes and return effects. The example assumes equal character to isolate basis selection. If the lots have different holding periods, the rate comparison can change and must be computed from the actual dates.
Selecting the higher-basis lot also leaves the lower-basis lot for a future disposition. It shifts the timing of embedded gain rather than eliminating the $15,000 difference from the portfolio. Compare expected future liquidity needs, character, and tax rates before deciding which eligible instruction serves the owner’s plan. The immediate compliance question is whether the desired selection was actually made through the required procedure.
Put the instruction into the transaction workflow
Ask the broker which identifiers it accepts, how it records the selection, and whether it permits per-transaction choices or only a particular standing method. Record the instruction and obtain evidence of its effective time. If the broker offers only one identification method, the IRS guidance treats that method as a standing instruction and does not permit the taxpayer to use a different method after 2025. Confirm platform capability before placing the trade.
A qualifying standing instruction can avoid making a separate manual selection for every transaction, but it must be in place with the broker by the required time and use sufficiently specific broker-designated identifiers. Maintain the order history and any revisions. A preference saved only in external tax software, or an adviser’s email never delivered to the custodial broker, should not be treated as proof of a broker instruction.
Reconcile defaults and retain the remaining-lot file
If no adequate identification applies, the default rule generally uses the earliest-acquired units of that asset in the relevant custody account. Preserve original acquisition dates when units move between wallets or accounts; the date of an inbound transfer does not necessarily become a new acquisition date. Reconcile the broker’s reported selection with the taxpayer’s evidence before preparing the disposition schedule.
Maintain a ledger showing units acquired, selected, sold, transferred, and remaining, with basis and holding period attached to each lot. Include transaction identifiers, account locations, and any adjustments. Where a broker has incomplete history for transferred units, a timely selection does not manufacture missing basis evidence. The identification file and the cost-support file must both be adequate for the return result claimed.
Before using the expected sale proceeds to fund an operating-year tax payment, compare the planned lot selection with the instruction that will actually govern. In the example, a $6,000 gain projection is unsupported if the transaction instead defaults to the $24,000 lot. Build the broker instruction into the approval checklist for the trade, then reconcile the confirmation promptly while account records are accessible and any discrepancy can be investigated.
Sources & further reading
Consult the original guidance and its effective dates. These references support the educational discussion; their application depends on the specific facts.