TaxSlayer 1099-B CSV Import — Format, Headers, and the Workaround

You picked TaxSlayer because it was the cheapest software that still says "imports 1099-B" on the feature list. You navigated to the investment section, found the Upload CSV button, picked your broker's export, and got back:

"Unable to process file. Please verify the file is in the correct format and try again."

The CSV opens fine in Excel. The data looks right. TaxSlayer's help page says CSV import is supported. But the upload keeps failing, and the help docs don't tell you what format the CSV actually needs to be in.

TaxSlayer Classic and Premium both accept 1099-B CSV imports, but they're particular about column headers, date formats, and how wash sales are encoded. The good news: once you know what TaxSlayer expects, reshaping your broker's CSV takes about five minutes. The better news: if you don't want to deal with column-renaming, you can convert the 1099-B PDF directly into a TaxSlayer-ready CSV and skip the manual reformatting step. This guide covers what TaxSlayer's CSV format requires, the errors that hit most users, and when to fall back to the PDF route.

What TaxSlayer Does With Your 1099-B

TaxSlayer offers three product tiers: Simply Free, Classic, and Premium. Investment income (1099-B, 1099-DIV, capital gains) requires Classic or Premium. The flow lives at Federal Section → Income → Investments (Capital Gains and Losses) → Form 1099-B – Sale of Investments.

From there you have three paths:

1. Manual entry: type each transaction into the form. Works fine for a handful of trades; tedious past 30.
2. CSV upload: drop a properly-formatted CSV with all your sales.
3. Broker auto-import: limited list of supported brokers (smaller than TurboTax's), but works cleanly when your broker is on it.

TaxSlayer's broker auto-import covers the major names (Fidelity, Schwab, Vanguard, TD Ameritrade, E*TRADE) but skips many neobrokers and any broker that requires multi-factor auth on the import. When auto-import doesn't apply, CSV is the workhorse path — much faster than manual entry for any account with more than a few trades.

The TaxSlayer CSV Format — Exact Headers and Order

TaxSlayer's CSV importer expects these columns, in this order:

Header	Description	Format
Description	Security name and quantity	"100 sh. AAPL"
Date Acquired	Purchase date	MM/DD/YYYY or "Various"
Date Sold	Sale date	MM/DD/YYYY
Proceeds	Gross sales amount (no $ or commas)	1234.56
Cost Basis	Cost basis (no $ or commas)	1000.00
Adjustment Code	Single letter (W, B, T, etc.)	"W" or blank
Adjustment Amount	Dollar adjustment (signed)	-50.00 or blank
Reporting Category	A, B, C, D, E, or F	Single letter

A few format rules:

• Headers must match exactly — character for character, including spacing. "Date Acquired" works; "Acquisition Date" does not. "Cost Basis" works; "Cost or Basis" does not.
• No dollar signs or commas in numeric fields. 1,234.56 and $1234.56 both fail validation. Strip them before saving.
• Dates in MM/DD/YYYY only. Two-digit years (3/15/26), date-first European formats (15/03/2026), and long formats (March 15, 2026) all fail.
• "Various" is allowed only in Date Acquired, never in Date Sold.
• Reporting Category is a single letter matching the Form 8949 reporting box: A (short-term covered), B (short-term noncovered), C (short-term not reported), D (long-term covered), E (long-term noncovered), F (long-term not reported).
• Blank wash sale loss disallowed column: unlike H&R Block, TaxSlayer doesn't have a separate Wash Sale Loss Disallowed field. Instead, code wash sales as Adjustment Code = "W" and put the disallowed loss as a negative number in the Adjustment Amount column. This is the format difference that catches most TaxSlayer users.

Reshaping Your Broker's CSV for TaxSlayer

Your broker's CSV almost certainly doesn't match this format out of the box. Schwab, Fidelity, Robinhood, and others each use slightly different column names, orders, and adjustment conventions. To convert:

1. Open the broker CSV in Excel or Google Sheets.
2. Rename the header row to match TaxSlayer's exact column names. Don't fuzzy-match — "Sales Proceeds" → "Proceeds", "Cost or Basis" → "Cost Basis", etc.
3. Reorder columns so they appear in the sequence above. TaxSlayer is generally tolerant of column order, but having them in the expected positions reduces ambiguity if the importer logs an error.
4. Strip dollar signs and thousands separators from Proceeds and Cost Basis columns. In Excel: select the column → Format Cells → Number with 2 decimals, no thousands separator → save as CSV.
5. Convert dates to MM/DD/YYYY. In Excel: =TEXT(A1, "MM/DD/YYYY") on the date columns.
6. Convert wash sale columns if your broker reports them in a separate Wash Sale Loss Disallowed field: copy that value (positive number) and put the negated value (-50.00 from a 50.00 disallowed loss) into Adjustment Amount, and set Adjustment Code to "W".
7. Map the reporting box to a single letter. If your broker's CSV says "Short-term covered" or "Box A", convert to just "A".
8. Save as .csv (not .xlsx).

This is mechanical but tedious. For accounts under ~50 transactions it takes 10 minutes; above 200 it's an hour and you're doubling back to fix typos. At that point, converting the 1099-B PDF directly into a TaxSlayer-shaped CSV is faster.

Common TaxSlayer Import Errors

"Unable to process file"

Generic — usually a header mismatch or encoding issue:

• Header typo or wrong order: re-check against the table above.
• BOM byte at file start: some Excel exports add a Unicode marker that TaxSlayer treats as part of the first column header. Open in a plain text editor (TextEdit, Notepad), confirm the first line starts with "Description" and nothing else, resave as UTF-8 without BOM.
• Quoting issue with commas in Description: a security like "Berkshire Hathaway, Class B" has an embedded comma. Wrap the Description field in double quotes: "Berkshire Hathaway, Class B". Excel does this automatically when you save as CSV, but it can get lost if you've been editing in a plain text editor.

"Date format invalid"

The Date Acquired or Date Sold column has an entry not in MM/DD/YYYY format. Common offenders:

• ISO 8601 (2026-03-15)
• Two-digit year (3/15/26)
• European order (15/03/2026)
• Excel auto-formatting that displays one way but stores another (right-click → Format Cells to confirm the stored format)

Reformat in bulk with Excel's TEXT function, save again, retry upload.

"Adjustment code not recognized"

TaxSlayer accepts single-letter codes: W (wash sale), B (basis correction), T (transferred basis on inheritance), L (nondeductible loss), Q (QSBS exclusion), S (collectible sale), N (nominee), R (rolled gain), E (corporate action). Multi-character codes (WB, WS) sometimes fail — split the transaction into two rows with one code each, or pick the dominant code and document the rest in your supporting records.

"Proceeds and basis don't reconcile with adjustment"

For wash sale rows (code W), TaxSlayer validates that:

• The adjustment amount is negative (reducing the loss).
• The adjustment magnitude doesn't exceed the loss being adjusted.

If your broker's CSV has the disallowed loss as a positive 50.00 and you forgot to negate it before putting it in Adjustment Amount, the validator fails. Always sign-flip when moving from a "Wash Sale Loss Disallowed" column to TaxSlayer's adjustment amount column.

"File too large"

TaxSlayer Online caps around 2,000-2,500 rows per upload before timing out. Split larger files into chunks of ~1,500 rows and upload sequentially. They'll appear as separate Form 8949 sections but math rolls up correctly to Schedule D. The large 1099-B walkthrough covers volume management options including the summary method.

When Auto-Import Works (and When It Doesn't)

TaxSlayer's broker auto-import covers a smaller list than TurboTax. Confirmed brokers include Schwab, Fidelity, Vanguard, TD Ameritrade (legacy), E*TRADE, Merrill, Wells Fargo, and a handful of others. If your broker is in the dropdown, sign in and let it pull — same workflow as any other product.

Notable gaps:

• Robinhood: not currently in TaxSlayer's auto-import list. CSV upload is the path. The broker exports a clean CSV that needs the wash sale column converted to TaxSlayer's adjustment format.
• Webull, M1, Public, Stash, and other Apex-cleared brokers: TaxSlayer doesn't have an Apex Clearing direct partner. Use CSV upload, or convert the Apex 1099-B PDF.
• Interactive Brokers: not in auto-import for TaxSlayer. CSV or TXF (Premium only) is the path.
• Crypto exchanges: TaxSlayer has a separate crypto reporting section. Don't try to import a 1099-DA through the equity 1099-B flow.

TXF Import (TaxSlayer Premium Only)

If you have a TXF export from your broker (TradeStation, Interactive Brokers), TaxSlayer Premium accepts it through File → Import → TXF File. This is the cleanest path for active traders with thousands of rows because TXF carries all the IRS metadata (reporting box, basis, adjustments) cleanly without column-renaming.

Classic doesn't have TXF import — you need Premium ($32.95+ vs Classic at $22.95 as of recent pricing). If you have a TXF and you're on Classic, you have two options: upgrade to Premium, or convert the TXF to a TaxSlayer-formatted CSV and upload that.

The CSV vs TXF vs Excel format breakdown covers when each format is the right pick.

When Your CSV Won't Cooperate

If you've reshaped your broker's CSV three times and TaxSlayer still won't accept it, the universal fallback is to convert the 1099-B PDF directly into a CSV pre-formatted for TaxSlayer. This sidesteps the broker-export inconsistencies (every broker exports differently; the PDFs are more standardized) and produces a file with TaxSlayer's exact expected headers.

The PDF-to-CSV guide covers the general workflow. The TaxSlayer-specific outputs are the same as TurboTax-format CSV with the adjustment code column conventions noted above.

Military and Student Filers — Free Options

TaxSlayer is a longstanding MilTax partner — active-duty military, National Guard, and reserves can file federal and state returns for free through MilTax (powered by TaxSlayer). The Premium tier features (including TXF import and full investment support) are included free for eligible service members.

To access: go to militaryonesource.mil/MilTax and follow the link to TaxSlayer. The product is identical to retail TaxSlayer Premium — same import paths, same forms, same support — just at $0.

For students filing simple returns, TaxSlayer Simply Free covers W-2 income but does not include the 1099-B section. If you have any investment sales to report (selling RSU shares, brokerage activity from a custodial account converting at age of majority, etc.), you need at least Classic. The MilTax path is the cheapest if you're eligible; otherwise Classic at ~$23 is the lowest tier that handles 1099-B.

FAQ

Does TaxSlayer support 1099-B CSV upload on the free tier?

No. TaxSlayer Simply Free does not include the 1099-B / Form 8949 section. You need Classic ($22.95) or Premium ($32.95) for any investment income. The MilTax partnership gives eligible military filers Premium for free.

My broker's CSV has a "Wash Sale Loss Disallowed" column. How do I map it to TaxSlayer's format?

TaxSlayer doesn't have a dedicated wash sale field — instead, code wash sales as Adjustment Code = "W" and put the disallowed loss as a negative number in the Adjustment Amount column. A 50.00 in your broker's wash sale column becomes -50.00 in TaxSlayer's Adjustment Amount with code W. Forgetting to negate is the most common cause of TaxSlayer's "adjustment doesn't reconcile" error.

Does TaxSlayer accept TXF imports?

Only the Premium tier does. Classic and Simply Free do not. If you have a TXF file and you're on Classic, either upgrade to Premium or convert the TXF to a CSV in TaxSlayer's expected format.

TaxSlayer keeps rejecting my CSV. What do I try first?

Re-check the header row character-for-character against the format table above. The most common failures are: (1) header typo or wrong order, (2) date format not MM/DD/YYYY, (3) dollar signs or commas in numeric fields, (4) wash sale loss in the wrong column with the wrong sign. Fix one variable at a time and re-upload between each fix.

Can I import multiple 1099-Bs from different brokers in one upload?

Yes — concatenate them into a single CSV with one header row at the top. TaxSlayer treats them as a single import. Make sure the column structure is consistent across all the broker-source CSVs after you reformat them, or you'll get partial-import errors.

My TaxSlayer upload succeeded but the transaction count is short. What happened?

Two likely causes: (1) some rows failed validation silently and were skipped (check the import summary for warnings about specific row numbers), (2) you hit the per-upload row cap and the file was truncated. Compare the imported count against the row count in your source CSV. If short, split the file and upload in chunks.

Does TaxSlayer accept summary totals for Form 8949?

Yes. In the same investment section, you can enter aggregate totals for Box A and Box D unadjusted lots, then attach the detailed 1099-B as a supplemental statement. This is identical in spirit to the TurboTax summary method and the IRS rules are the same: only works for covered transactions without adjustments.

Bottom Line

TaxSlayer's CSV importer works but is unforgiving about exact column names, date formats, and the way wash sales are encoded. Get the headers right (compare to the table above), strip currency formatting from numeric columns, and remember to flip the sign on wash sale adjustments — TaxSlayer wants negative numbers, not the positive "disallowed loss" most brokers export.

When the CSV reformatting takes longer than it should, convert the 1099-B PDF directly into a TaxSlayer-shaped CSV. The output is a single file with the exact headers and conventions TaxSlayer expects, no broker-by-broker quirks to debug. Military filers get TaxSlayer Premium free via MilTax, which is the cheapest path to full TXF and CSV import support for active duty.

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TaxSlayer rejecting your CSV? Convert your 1099-B free — drop in the PDF, get a CSV with TaxSlayer's exact headers and wash sale signing already done. Three free conversions per month, no broker credentials shared.