Missing Tax Documents: What to Do Before Filing

When tax documents are missing before filing, sort each one into two groups. Some can be rebuilt from other records the client already has, such as a December statement or an online account. Others hold figures only the issuer knows, such as a K-1 or cost basis, and are worth waiting for. Record whichever path you take.

Which missing tax documents can be rebuilt from other records?

Missing tax documents that can be rebuilt are the ones whose figures also appear somewhere else the client can reach. Interest, mortgage interest, wages and estimated payments usually show up on a year-end statement, a final pay stub, a lender or bank website, or the client's IRS online account. The substitute gives the figure while the form is requested.

Common substitutes, by document:

• 1099-INT. The December statement or the bank's online year-end summary usually shows interest paid for the year. The IRS Instructions for Form 1099-INT set the filing trigger at $10 of interest, so a small amount may never produce a form at all, and the statement is the only record.
• 1098. The lender's website or the December mortgage statement often shows year-to-date interest. A later section covers this one in detail.
• Estimated payments. The IRS page on your online account says it shows up to five years of payment history, including estimated tax payments. Bank statements show the same debits.
• W-2. A final pay stub shows year-to-date pay and withholding, but a missing W-2 has its own IRS procedure. The IRS page about Form 4852 describes that form as a substitute for Form W-2, Form W-2c and Form 1099-R. The post on how to file taxes with a missing W-2 covers it rather than this one.
• 1099-G for a state refund. The state tax agency's records, or last year's state return, show the refund amount.

A substitute is a source for a figure, not a replacement for asking. Keep requesting the form. When it arrives, compare it with the figure used. If they match, note that and move on. If they do not, the firm knows before filing, not after.

Some documents look rebuildable and are not. A December brokerage statement may list sales, but the basis detail the broker reports sits on the tax form. The post on a missing 1099-B covers brokerage forms, and the tax forms and payroll category covers reading each form once it arrives.

Missing tax documents only the issuer can supply

Missing tax documents only the issuer can supply are those whose figures exist nowhere else: Schedule K-1s, corrected forms, and cost basis on sales. The client cannot rebuild a partnership's allocation, guess what a payer will correct, or reconstruct basis that only the broker tracked. For these, the request goes to the issuer, and the timing is theirs.

Schedule K-1. The partner's share of income, deductions and credits comes from the partnership's own books, so there is no client record to substitute, and a partnership on extension can send its K-1 months after the individual deadline. The issue dates by entity type are set out in when K-1s are issued by entity type.

Corrected forms. The IRS General Instructions for Certain Information Returns say a filer marks the CORRECTED box when fixing a form already filed or furnished, and must furnish the corrected statement to the recipient. A client who has heard a correction is coming, often from a brokerage, may be told to expect it after the original. The original's figures are about to change.

Cost basis. The IRS Instructions for Form 8949 (2025) say to report the proceeds shown on Form 1099-B or 1099-DA, and to report the basis shown when the form says basis was reported to the IRS, making any adjustment in column (g). When the form or the basis detail is missing, the sale's proceeds may show on a statement, but the basis the broker reported does not.

The request for these is a direct one: ask the client to contact the issuer, or to check the issuer's website for a posted form. The post on how to get clients to send tax documents covers wording a request clients act on, and the post on client document reminders covers timing a follow-up.

Missing 1098 mortgage interest statement

A missing 1098 mortgage interest statement can usually be covered by the lender's website or the December mortgage statement, which often show the year's interest. Ask the client to download the 1098 from the servicer's site first. If it is not posted, the year-to-date interest on the last statement gives the figure while a copy is requested.

The IRS Instructions for Form 1098 say lenders file for $600 or more of mortgage interest received during the year in the course of their business, and that the threshold applies separately to each mortgage. The General Instructions for Certain Information Returns list January 31 as the date Form 1098 is due to the borrower, which for tax year 2025 forms was February 2, 2026, because January 31 fell on a Saturday.

Three situations explain most missing 1098s:

1. The loan was sold or transferred. Servicing moved mid-year, so the client may need paperwork from both servicers. The client often has one and not the other.
2. The loan was refinanced or paid off. The old lender's final form covers the months before payoff, and the client may not expect it.
3. The lender is not a business that files. A loan from a family member or a seller may produce no 1098 at all.

The return has places for each case. The IRS Instructions for Schedule A (2025) say line 8a is for mortgage interest and points reported on Form 1098, and line 8b is for interest paid to a recipient who did not provide a Form 1098. For a rental, the Instructions for Schedule E (2025) put interest paid to banks or financial institutions on line 12, and interest where the recipient was not a financial institution or no Form 1098 was received on line 13. Which line applies is the preparer's decision; the document request just has to find out which situation it is.

When should a preparer stop and wait for a missing tax document?

A preparer should stop and wait for a missing tax document when an estimate would create more work than it saves: the figure is large, only the issuer knows it, or a correction is already expected. A K-1, a brokerage form with basis detail, or a form the issuer has said will be corrected usually belongs in this group.

Signs that waiting is the better choice:

• The figure drives other figures. A K-1 can affect several lines and forms. An estimate there is not one number but many.
• A correction is announced. Filing on the original when the issuer has said a corrected form is coming means an amended return is likely.
• The client has no record at all. No statement, no website, no prior-year pattern to check against.
• The amount is large relative to the return. A small interest form is one thing; a large distribution is another.

Signs a substitute is enough to proceed:

• The figure appears on a statement or online account in the same amount the form would show.
• The amount is small and the source is clear.
• The form is late for a known reason, such as a servicing transfer, and the statement covers it.

When waiting runs into the deadline, an extension is the usual tool. The post on filing an extension because of missing documents covers that decision; this post does not.

Knowing early which documents are missing is what makes waiting possible. Schema CPA checks each client's arrivals against last year's documents and flags what has not come, so a missing K-1 for tax year 2026 is visible in February 2027 rather than found on April 10, 2027. The client tracker demo shows a sample client's missing lines.

Mistake: filing with a guessed figure and no note in the file

Filing with a guessed figure and no note in the file is the mistake that turns a late form into a hard problem. When the real form arrives months later and differs, nobody can tell what the return used, where the number came from, or whether the difference matters. A short note written at filing time answers all three.

Record four things whenever a figure comes from anything other than the issuer's form:

1. The source used. "December statement, Harbor Federal, account XXXX-4821, year-to-date interest."
2. The figure used. The exact amount entered.
3. The date. When the substitute was used and the form was still missing.
4. The follow-up. Who is watching for the form, and what happens when it arrives.

When the form arrives, compare and close. If it matches, write "2026 Form 1098 received March 30, 2027, matches statement figure." If it does not, the note shows exactly what changed. The IRS page about Form 1040-X describes that form as the way to correct a filed Form 1040; whether an amendment is needed is the preparer's call, and the note makes the call quick.

A related slip is using the substitute and then forgetting to keep asking. Once a figure is in the return, the missing form stops feeling urgent, and the line drifts from missing to ignored. Leave the tracker line open, with a status that says a substitute was used, until the form itself arrives or the firm decides in writing that it will not come.

Keep the note with the client's documents, not in someone's inbox. A note in the tracker line for that document, beside the received date, survives staff changes.

A decision table for common missing forms

Example only. The table describes typical substitute sources and how firms often treat each form. It is not tax advice, and the preparer decides each case.