How to Find Potential Tax Losses in Your Portfolio

Updated September 26, 2026.

To find potential tax losses, review individual tax lots in taxable accounts rather than relying only on a portfolio's total return. A profitable position can contain a losing lot, and a recent price decline can still leave every lot above basis. Software can help organize the review, but the institution's records and the household's circumstances determine what needs further investigation.

This guide focuses on finding and validating candidates. It does not recommend selling a particular investment. For choosing a service, use the tax-loss harvesting software buying guide.

Why the summary screen can hide a candidate

Suppose an investor owns two lots of the same hypothetical stock, now worth $90 per share:

The position is profitable overall, but one lot shows a loss. That is an invitation to review the lot, not proof that selling it is appropriate or that the loss will be deductible. The illustration assumes the stated basis is correct and ignores transaction costs and other adjustments.

The reverse can happen too. A stock that fell from a recent high may remain above your purchase basis. A “down this month” filter is therefore different from a tax-loss review.

Step 1: identify the accounts relevant to the question

Start with taxable investment accounts and their ownership. Keep retirement accounts in the broader activity review where relevant, but do not assume a decline inside an IRA creates a deductible capital loss like a taxable sale.

List every account you intend to include and any information you cannot access. A household view is valuable when it reveals a gap instead of concealing one behind a total balance.

Step 2: gather the actual lots

For each candidate position, obtain acquisition dates, quantities and adjusted basis from the institution. Review transferred positions carefully because displayed information may be incomplete. Distinguish a current estimate from a finalized transaction record.

Ask the brokerage how lot selection works for the exact security and account. Do not assume that selling a number of shares automatically uses the lot you had in mind. The identification and confirmation process is an implementation question for the institution.

Record the data date. A price can change before a decision is made, so an estimated loss is not a guaranteed execution result.

Step 3: separate data problems from investment losses

A blank basis field is not a zero-cost investment by default. A dramatic loss may reflect a transfer, split or other record issue rather than the economic result you think you are seeing. Reconcile the position with source documents before ranking it as an opportunity.

A useful review list should contain a status, not just a dollar figure:

A candidate can move backward if new information appears. That is a useful correction, not a failure of the process.

Step 4: review the tax context

A loss is not a dollar-for-dollar tax saving. How it is used depends on the return and applicable rules. Wash-sale restrictions involve substantially identical purchases during the 30 days before or after a loss sale, including certain activity beyond the selling account. IRS Publication 550

Use the cross-account wash-sale checklist to gather the relevant activity. Do not rely on a replacement ticker's name or a software badge to settle uncertain treatment.

A qualified tax professional can help evaluate how a potential allowable loss interacts with gains, carryforwards and other facts. The useful output at this stage may be a question to resolve rather than a number to optimize.

Step 5: review what the portfolio would become

Would a sale change an exposure you intend to keep? Would the resulting allocation still fit the goal? What costs and implementation issues would be involved? Is this an investment you were already considering changing, or is the tax figure driving the entire decision?

Doing nothing belongs in the comparison. A candidate loss may be too small to justify complexity, or the investment implications may outweigh the expected benefit. The goal is a coherent portfolio and financial plan, not the maximum count of harvested losses.

How Mezzi can help organize the question

Mezzi brings supported investments together with banking, liabilities and manually entered assets, while AI Personalization supplies goals and preferences. That can help connect a potential loss review to a cash need or an allocation concern. Mezzi account groups

Ask: “Which information would be needed to evaluate this lot, and how might the decision affect my wider plan?” Check that the answer distinguishes visible information from assumptions.

A connection does not guarantee full lot-level data, every household transaction or real-time information. Mezzi provides guidance rather than executing a sale or certifying a loss as deductible. Its current plans describe the product scope.

Keep the result useful after the conversation

Save the source records, the candidate list and unresolved questions. If a transaction is ultimately chosen, retain the institution's confirmation and reconcile the actual result with the original estimate. Continue reviewing relevant subsequent activity and final tax records.

Finding a hidden lot-level loss is only the beginning. A useful tool helps turn that discovery into a decision whose inputs, consequences and responsibilities are clear.

Frequently asked questions

Can a position with an overall gain contain a tax loss?

Yes. Individual lots can have different acquisition costs. A combined gain can conceal a lot below its adjusted basis, though tax treatment and investment suitability still need review.

Does a decline from a recent high mean I have a deductible loss?

No. Compare value with the relevant adjusted basis, not only a recent market price. A loss generally must be realized and satisfy applicable rules to affect the return.

Can Mezzi guarantee that it finds every losing tax lot?

No complete tax-lot coverage guarantee is established here. Verify the available data against institution records and identify missing accounts or adjustments.

Should I sell every lot showing a loss?

No. Review the tax circumstances, relevant purchases, investment exposure, costs and alternatives. A candidate is a starting point for analysis, not a trade instruction.