Can AI do my investment taxes?

Last updated August 2026

Short answer

AI is useful for investment tax in a narrow, valuable way: explaining what the rules say, reading your forms with you, and pointing at figures that look wrong. It does not file, it does not sign, and it does not carry the liability. The highest-value use is checking cost basis and hunting for wash sales your broker cannot see, because both are errors that survive into a filed return and both cost money in the same direction.

Investment tax is unusual among tax problems: the rules are stable and published, and the errors are concentrated in a few predictable places. That combination suits a machine that reads carefully.

What it does reliably

Explaining a rule in the context of your situation. The wash sale rule, the holding period that separates long-term from short-term treatment, what makes a dividend qualified: all published, all frequently misunderstood.

Reading a consolidated 1099 with you, box by box, and saying what each figure represents. Proceeds are not gain, and people panic at the proceeds line every year.

Modelling a decision before you take it. What selling a lot would realise, what the difference between selling now and selling after the one-year mark is worth, what a loss can offset.

Where the errors actually are

Cost basis on non-covered securities, which the broker was never required to track. Older holdings, shares transferred in from another broker, inherited shares and gifts all land in this category.

Inherited shares usually take a stepped-up basis to the value at the date of death. A 1099-B carrying the original purchase price overstates the gain, sometimes by a lot.

RSU and ESPP sales, where the compensation element already taxed through your W-2 is frequently left out of basis. Filing that unchanged means paying tax twice on the same money.

The wash sale blind spot

A wash sale happens when you sell at a loss and buy the same or a substantially identical security within 30 days either side. The loss is disallowed and added to the basis of the replacement shares.

Your broker applies this within its own account and cannot see the rest of your life. Selling at Broker A and rebuying at Broker B produces a wash sale that appears on neither statement.

The version with real teeth is a repurchase inside an IRA, where the disallowed loss is lost permanently rather than deferred. Software that can see all your accounts at once is the natural place to catch this.

Try it in Walnut

Walnut reads your connected brokerage positions across accounts, which is the vantage point a single broker's tax form does not have.

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What it should not be trusted with

Anything where the answer depends on facts it cannot verify: your filing status, your other income, state treatment, or a document you have not shown it.

Anything numerically precise that you have not checked against the source. Ask where a figure comes from, then look at the IRS page or the form itself.

Anything that is genuinely a judgment call under an unsettled rule. That is what a professional is for, and the fee is small next to the amounts involved.

A workable division of labour

Use software to understand the forms and find the suspicious lines before filing season, when there is still time to fix them.

Use tax software or a preparer to file, and hand them the specific corrections you found rather than expecting them to find them.

Keep your own records for anything non-covered. No amount of intelligence reconstructs a purchase price nobody wrote down.

Sources

The wash sale rule, cost basis reporting and the 1099 series are covered by the IRS in Publication 550. Holding periods and rates are in Topic no. 409, and the form itself in About Form 1099-B. Walnut is informational and is not an investment adviser. This guide is educational and not personalized tax advice; anything with a tax consequence is worth confirming with a tax professional.

FAQ

Can AI file my tax return?

Not by itself. Filing happens through tax software or a preparer who signs the return. What AI can do is the reading around it: explaining what a form says, checking whether a figure looks wrong, and telling you which question to ask.

Who is liable if the AI gets it wrong?

You are. A signed return is your statement to the IRS regardless of what produced the numbers. A paid preparer carries their own responsibilities and can represent you, which is a real difference worth paying for once amounts get large.

What is the single most useful thing to ask it?

Whether your cost basis is right. Brokers frequently report basis that is blank or wrong on transferred, inherited and equity-compensation shares, always in the direction that costs you money, and it is the error a careful reading catches.

Can it catch a wash sale my broker missed?

It can flag the possibility, which is more than your broker will. Brokers only see their own accounts, so a wash sale created across two brokers, or by a purchase inside an IRA, appears on neither 1099-B. Identifying it is the taxpayer's responsibility.