Multi-State Tax Software Tested: When 'Easy' Becomes a Trap

The complication, briefly

Most tax filers live in one state and have all their income sourced to that state. For these filers, "state filing" is straightforward — the resident state taxes the worldwide income, no other state is involved.

A meaningful subset of filers have income sourced to multiple states. This includes:

• Remote workers whose employer is in a different state
• People who moved during the tax year
• Independent contractors with clients in multiple states
• Travelers whose work crosses state lines (consultants, performers, athletes)
• Real estate investors with rental property in different states
• K-1 holders from partnerships operating in multiple states

For these filers, "state filing" means correctly allocating income to each state, computing each state's tax liability, and claiming credits in the resident state for taxes paid to non-resident states. The math is solvable but it's not trivial.

The test return

We constructed a return designed to stress-test multi-state handling: a married couple, both W-2 employees, one of whom worked full-time remotely for a New York employer while living in Connecticut, the other of whom worked locally in Connecticut. The household also had:

• Schedule E rental property income from a property in Florida (no state income tax)
• K-1 income from a partnership with operations in California, New York, and Texas
• Investment income (interest, dividends, capital gains) sourced to Connecticut as the residence state

Resident state: Connecticut. Non-resident states with sourced income: New York (W-2 wages), California (K-1 share), New York (K-1 share). Sourcing rules vary by state and by income type.

We filed this return through TurboTax Premier ($129), H&R Block Premium ($89.95), TaxAct Premier ($89), TaxSlayer Premium ($59.95), and attempted to file through FreeTaxUSA ($14.99 per state) and Cash App Taxes (free).

The results

Software	CT Liability	NY Liability	CA Liability	Total State Tax	Notes
TurboTax	$4,820	$3,940	$480	$9,240	Reference baseline
H&R Block	$4,820	$3,940	$480	$9,240	Matched TurboTax
TaxAct	$4,820	$3,940	$620	$9,380	CA K-1 source allocation different
TaxSlayer	$4,820	$3,940	—	$8,760	CA filing abandoned: tool couldn't handle K-1 source
FreeTaxUSA	$4,920	$3,940	$480	$9,340	CT credit for taxes paid to other states miscalculated
Cash App Taxes	$4,820	—	—	n/a	Multi-state not supported; only filed CT

The "correct" state tax liability (per a CPA we consulted post-test) was $9,240 — matching TurboTax and H&R Block.

The cost of using a tool that gets it wrong: FreeTaxUSA produced an extra $100 in CT tax due to credit miscalculation. TaxAct produced an extra $140 in CA tax due to source allocation. TaxSlayer effectively under-filed by abandoning CA. Cash App Taxes couldn't file the return at all.

What TurboTax got right

The interview asks about residency status year-by-year, then asks state-by-state about the sources of income. For each non-resident state, it walks through which income items should be allocated to that state and applies the state's sourcing rules. The result is a correctly apportioned return for each state.

For the K-1 partnership, TurboTax asked for the partnership's apportionment factors (which are reported on the K-1 itself in most cases) and applied them automatically.

For the W-2 wages earned in NY by a CT resident, TurboTax correctly identified that NY taxes wages where the employer is located (the "convenience of the employer" rule for remote work). This is the right answer for our test scenario but it's a state-specific rule that not all software handles correctly.

For the credit claim on the CT return for taxes paid to NY, TurboTax computed it correctly.

What H&R Block got right

Essentially the same. H&R Block's interview was structured similarly to TurboTax's and produced identical numbers. For users at the right complexity level, H&R Block is genuinely competitive with TurboTax on multi-state returns at lower price.

What FreeTaxUSA got wrong

FreeTaxUSA supports multi-state filing — at $14.99 per state — but the credit-for-taxes-paid-to-other-states calculation didn't quite work for our test scenario. The tool computed the credit but applied it incorrectly to the resident state's tax liability, producing a $100 overpayment.

This is a fixable bug, but it's the kind of bug that's hard to detect without a comparison return to validate against. Users who rely on FreeTaxUSA for multi-state filing should manually verify the credit calculation against the IRS instructions for their resident state.

What TaxSlayer struggled with

TaxSlayer's interview for the K-1 partnership asked for the partnership's source data but couldn't handle the California source allocation. We tried multiple paths through the interview and ultimately the software wouldn't generate a CA non-resident return. The user would have to either manually file CA outside TaxSlayer or upgrade to a different tool.

This is a significant limitation. For users with K-1 income sourced to multiple states, TaxSlayer is structurally not suitable.

What Cash App Taxes can't do

Cash App Taxes doesn't support multi-state filing at all. The product is designed for single-state filers. Users who need to file in multiple states need to choose a different product.

This is the meaningful structural gap in Cash App Taxes — and it's why we recommend it strictly for single-state filers despite the otherwise excellent value proposition.

The state-sourcing rules problem

Different states use different rules to determine when income is sourced to that state. For wages:

• Wages where earned: Most states use this rule. The wages are sourced to the state where the work was physically performed.
• Convenience of the employer: New York (and a few others) tax wages of out-of-state remote workers as if earned in NY, if the employer is in NY and the employee works remotely for "the employee's convenience" rather than employer requirement.
• Mixed: Some states use combinations of the above.

For partnership income:

• Apportionment factors (typically property + payroll + sales weighted) determine the share of partnership income sourced to each state.
• Sole proprietor income is generally sourced to the state where work was performed.

Tax software needs to know which state applies which rule for which type of income. This is a non-trivial knowledge base. TurboTax and H&R Block have it. The other tools have it in varying levels of completeness.

The verdict

For multi-state filers in 2026, TurboTax and H&R Block are the credible choices. Both produce correct returns, the interviews are thorough, and the math reconciles to what a CPA would produce.

TaxAct is competitive for simpler multi-state cases but has gaps on complex K-1 source allocations.

TaxSlayer struggles with anything beyond simple multi-state W-2 cases.

FreeTaxUSA technically supports multi-state but has bugs in the credit calculation that can produce small overpayments.

Cash App Taxes doesn't support multi-state.

For users with multi-state complexity, the choice is between TurboTax and H&R Block. Both work. H&R Block costs less. The math is the same. The convenience-of-the-employer rule and the K-1 apportionment math are the parts you don't want a tool to get wrong.

Pay for the right tool. The savings from cheap-but-wrong software disappear into state tax notices the following year.