SuperMoney logo
SuperMoney logo

What IRS Letter 3688 Means and How to Handle it

SuperMoney Team avatar image
Last updated 11/20/2024 by
SuperMoney Team
Fact checked by
Ante Mazalin
Summary:
The IRS Letter 3688 notifies taxpayers of penalties for a substantial understatement of income. This letter typically indicates discrepancies between reported income and IRS findings, often due to underreporting or misreported amounts. Addressing the notice promptly is critical to avoid penalties and resolve the issue effectively.
Struggling with IRS notices? If you’ve received an IRS letter and aren’t sure how to handle it, you might want to explore professional tax relief options. Optima Tax Relief has helped thousands of people resolve their tax issues and get back on track with the IRS. Learn more about how they can assist you with your situation.
Receiving IRS Letter 3688 can be an unsettling experience for taxpayers. This letter signals a potential issue with your reported income, specifically a significant understatement. The IRS issues this notification when it identifies discrepancies between what was reported on your tax return and the information it has on file. Addressing the issue promptly can help mitigate penalties and clarify any misunderstandings. In this article, we’ll break down everything you need to know about IRS Letter 3688, how to respond effectively, and the potential consequences of not addressing it.

Get Competing Personal Loan Offers In Minutes

Compare rates from multiple vetted lenders. Discover your lowest eligible rate.
Get Personalized Rates
It's quick, free and won’t hurt your credit score

What is IRS Letter 3688?

IRS Letter 3688 is an official notice sent to taxpayers when the IRS determines that their tax return includes a substantial understatement of income. This typically means that the reported income on your tax return is significantly lower than what the IRS believes you actually earned. This discrepancy may arise due to various reasons, such as:
  • Omitted income from sources like freelance work or side businesses.
  • Incorrect deductions or credits claimed on your tax return.
  • Clerical errors, either by the taxpayer or a tax preparer.
The letter informs you of the penalties that may apply, the next steps to take, and any deadlines for responding. Ignoring this notice can lead to further enforcement actions, including additional fines and legal proceedings.

Pro Tip

Set up IRS account alerts online to get real-time notifications on any changes to your tax return or account. This helps you stay updated on adjustments and due dates.

Why did you receive IRS Letter 3688?

The primary reason for receiving IRS Letter 3688 is the identification of a substantial understatement of income. According to the IRS, this occurs when the amount of income omitted exceeds 10% of the correct taxable income or $5,000, whichever is greater. This triggers an automatic penalty unless the taxpayer can provide adequate documentation or justification.
Some common causes include:

1. Income discrepancies

This happens when all income sources are not reported, such as contract jobs, investment earnings, or rental income. Third-party reporting from employers or financial institutions may reveal discrepancies.

2. Incorrect tax calculations

Claiming deductions or credits incorrectly or failing to update income totals accurately can result in errors that lead to a substantial understatement.

3. Misfiled or missing forms

Failure to attach required documentation, such as W-2s or 1099s, may prompt the IRS to reassess your tax liability, resulting in Letter 3688.

Pro Tip

Keep organized records of all income and deductions throughout the year. Having accurate documentation can help resolve discrepancies quickly if you receive IRS Letter 3688.

How does Letter 3688 affect you?

Receiving IRS Letter 3688 can have several implications:
  • Financial penalties: The IRS typically imposes a penalty of 20% of the understated tax amount.
  • Audit risk: Significant discrepancies may lead to a more in-depth examination of your tax returns.
  • Delayed processing: Any pending refunds or credits may be delayed until the issue is resolved.
Failing to respond promptly can exacerbate these issues, leading to compounding penalties and increased scrutiny from the IRS.

What should you do when you receive IRS Letter 3688?

When you receive IRS Letter 3688, follow these steps to address the issue:
  • Carefully review the notice to understand the reasons behind the substantial understatement penalty.
  • Compare the IRS findings with your tax return to identify discrepancies.
  • Gather documentation that supports your reported income and deductions, such as receipts, bank statements, and W-2 or 1099 forms.
  • Contact the IRS directly if you need clarification or believe there’s been a mistake.
  • Consult a tax professional or CPA for guidance on responding effectively.
  • Submit any required corrections or additional documentation within the deadline specified in the letter.

Pro Tip

Use IRS-approved tax software or hire a professional tax preparer to minimize the chance of filing errors that can trigger substantial understatement penalties.

How to avoid substantial understatement penalties

Avoiding penalties requires careful attention to detail and compliance with tax laws. Here’s how you can minimize risks:

1. Report all sources of income

Ensure that you report every source of income, no matter how small. Review all 1099s, W-2s, and other income statements before filing your return.

2. Double-check your deductions

Only claim deductions and credits you qualify for, and maintain documentation to support them in case of an audit.

3. Use reliable tax preparation tools

Consider using trusted tax preparation software or hiring a certified professional to reduce errors.

4. File accurately and on time

Submitting accurate and timely returns reduces the likelihood of discrepancies and penalties.
Looking for the best way to reduce your tax burden? We’ve compiled a list of the Best Tax Relief Companies to help you navigate tax challenges and save money. Click here to discover trusted experts who can assist you with tax resolution, IRS negotiations, and more!

Frequently asked questions

What is a substantial understatement penalty?

A substantial understatement penalty is a fine imposed by the IRS when a taxpayer significantly underreports their income or overstates deductions and credits. This penalty is typically 20% of the understated tax amount and is outlined in IRS Letter 3688.

Can I negotiate or reduce the penalty?

Yes, you can request a reduction or abatement of the penalty if you have reasonable cause for the understatement. Examples include reliance on professional advice, unforeseen circumstances, or documentation errors. To initiate the process, provide a written explanation and supporting evidence to the IRS.

How long do I have to respond to IRS Letter 3688?

The response deadline is usually stated on the letter. Typically, taxpayers have 30 days from the date of the letter to provide a reply. Failing to respond within this timeframe can lead to additional penalties or enforcement actions.

What should I do if I believe the IRS made a mistake?

If you believe there is an error in the IRS findings, gather evidence to support your claim. Contact the IRS using the contact information provided in Letter 3688. You may also seek assistance from a certified tax professional to help resolve the discrepancy.

Does receiving IRS Letter 3688 mean I am being audited?

Not necessarily. IRS Letter 3688 indicates a substantial understatement penalty due to discrepancies in your tax return. While it increases the likelihood of an audit, receiving this letter does not automatically mean an audit is underway.
Need help understanding other IRS letters and notices? Visit our comprehensive guide to IRS Letters and Notices or search for the document you received in the table below.
IRS Letter or Notice Number
Notice Description
CP01The IRS verified your claim of identity theft and will monitor your account.
CP01HThe IRS received a tax return with a social security number that belongs to a dead person.
CP02HMoney is due on an amended return based on a grant received due to Hurricane Katrina, Rita, or Wilma.
CP03CYou received the First-Time Homebuyer Credit for a house you purchased.
CP04You may be eligible for tax deferment because either you or a spouse served in a combat zone, a qualified contingency operation, or a hazardous duty station during the tax year specified on your notice.
CP08You may be entitled to additional money due to the Additional Child Tax Credit.
CP10Your tax return changed due to a miscalculation, and the refund you wanted to apply to an estimated tax payment has changed.
CP10AYour tax return changed due to a miscalculation of the Earned Income Credit, and the refund you wanted to apply to an estimated tax payment has changed.
CP11You owe money because the IRS amended your return due to a miscalculation.
CP11AYour tax return changed due to a miscalculation of the Earned Income Credit, and the refund you wanted to apply to an estimated tax payment also changed.
CP11MYour tax return changed due to a miscalculation of the Making Work Pay and Government Retiree Credit, and the refund you wanted to apply to an estimated tax payment has changed.
CP12You are due a bigger refund because the IRS corrected one or more mistakes on your tax return.
CP12AThe IRS made changes to correct the Earned Income Credit (EIC) claimed on your tax return.
CP12E or CP12FThe IRS corrected a miscalculation on your return.
CP12MThe IRS made changes to the computation of the Making Work Pay and/or Government Retiree Credits on your return.
CP12RThe IRS made changes to the computation of the Rebate Recovery Credit on your return.
CP13The IRS made changes to your return due to a miscalculation. There is no refund or amount due. Your balance is zero.
CP13AThe IRS made changes to your return due to a miscalculation of the Earned Income Credit. There is no refund or amount due. Your balance is zero.
CP13MThe IRS made changes to your return due to a miscalculation of the Making Work Pay credit or the Government Retiree Credit. There is no refund or amount due. Your balance is zero.
CP13RThe IRS made changes to your return due to a miscalculation of the Recovery Rebate Credit. There is no refund or amount due. Your balance is zero.
CP14You owe money on unpaid taxes.
CP16The IRS made changes to your return due to a miscalculation. The refund you were due was applied to other tax debts.
CP21AYou owe money due to the changes you requested that the IRS make on your tax returns.
CP21BYou are due a refund due to the changes you requested that the IRS make on your tax returns. The money should arrive within 2 to 3 weeks.
CP21CThe IRS made the requested changes to your tax return. You will not receive a refund, and there is no tax due. Your balance is zero.
CP21EAs a result of your recent audit, the IRS made changes to your tax return, and you owe money as a result of those changes.
CP21IThe IRS made changes to your tax return relating to the Individual Retirement Arrangement (IRA) taxes. You owe money due to the changes.
CP22AThe IRS made the changes you requested, and you owe money as a result.
CP22EAs a result of your recent audit, the IRS changed your tax return, and you now owe money.
CP22IThe IRS made changes to your tax return relating to the Individual Retirement Arrangement (IRA) taxes. You owe money due to the changes.
CP23The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. You owe taxes due to these changes.
CP24The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. This resulted in an overpayment of estimated taxes.
CP24EThe IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. This resulted in an overpayment of estimated taxes.
CP25The IRS changed your return because there was a difference between the amount of estimated tax payments listed on your tax return and the amount actually posted to your account. You are not due a refund, nor do you owe any money. Your balance is zero.
CP31You need to update your address because your refund check was returned to the IRS.
CP45The IRS was unable to apply your overpayment to your estimated tax as you requested.
CP49The IRS used all or part of your refund to pay a tax debt.
CP53Your refund check will be sent by mail because the IRS can’t provide your refund through direct deposit.
CP57The bank declined your payment, so the IRS was unable to draft funds from your bank account.
CP71A reminder of the amount you owe in tax, penalty, and interest.
CP71AA reminder of the amount you owe in tax, penalty, and interest.
CP71CA reminder of the amount you owe in tax, penalty, and interest.
CP71DA reminder of the amount you owe in tax, penalty, and interest.
CP88The IRS is holding your refund because you haven't filed one or more tax returns, and it believes you will owe tax.
CP90The IRS is notifying you of its intent to levy certain assets for unpaid taxes. You have the right to dispute the levy in a Collection Due Process hearing.
CP91The IRS will levy up to 15% of your social security benefits for unpaid taxes.
CP120The IRS needs documentation of your tax-exempt status.
CP120AYour organization’s tax-exempt status has been revoked because it failed to file a Form 990 series return for three consecutive years.
CP130You may no longer need to pay the Alternative Minimum Tax (AMT) because your tax return filing requirements changed.
CP152The IRS received your return.
CP153The IRS will send your refund by mail because your direct deposit did not go through.
CP161You have an unpaid balance due to the IRS.
CP166Your monthly payment to the IRS did not go through due to insufficient funds in your bank account.
CP178You may no longer owe excise tax because your tax return filing requirements changed.
CP231You need to update your address because your refund was returned to the IRS.
CP259You did not file the business tax return identified in the notice.
CP259AYou should have filed these forms but did not – Form 990/990-EZ, Return of Organization Exempt From Income Tax, or Form 990-N (e-Postcard).
CP259BThe IRS requires you to file these forms but did not – Form 990-PF, Return of Private Foundation or Section 4947(a)(1) Nonexempt Charitable Trust Treated as a Private Foundation.
CP259CThe IRS believes that you are a private foundation, but did not file the required Form 990-PF, Return of Private Foundation or Section 4947(a)(1) Nonexempt Charitable Trust Treated as a Private Foundation.
CP259DYou must file this form, but you did not – Form 990-T, Exempt Organization Business Income Tax Return.
CP259EYou should have filed this form, but you did not – Form 990-N (e-Postcard) or Form 990/990-EZ, Return of Organization Exempt From Income Tax.
CP259FThe IRS requires you to file this form but did not – Form 5227, Split-Interest Trust Information Return.
CP259GThe IRS requires you to file this form, but you didn’t – Form 1120-POL, U.S. Income Tax Return for Certain Political Organizations.
CP259HAs a tax-exempt political organization, you must file this form, but you did not – Form 990/990-EZ, Return of Organization Exempt From Income Tax.
CP276AYou submitted your tax liability schedule incorrectly. The IRS typically charges a Federal Tax Deposit (FTD) penalty for this but did not this time.
CP276BThe IRS did not receive the correct amount of tax deposits. It normally charges a Federal Tax Deposit (FTD) penalty but did not this time.
CP297The IRS is notifying you of its intent to levy certain assets for unpaid taxes. You have the right to dispute the levy at a Collection Due Process hearing.
CP297AThe IRS has levied your assets for unpaid taxes. You have the right to dispute the levy at a Collection Due Process hearing.
CP298The IRS notifying you of its intent to levy up to 15% of your social security benefits for unpaid taxes.
CP501You have a balance due on one of your tax accounts.
CP503You have an unpaid balance on one of your accounts, and the IRS has not heard from you.
CP504You have an unpaid amount due on your account. If you do not pay immediately, the IRS will levy your state income tax refund to apply it to the amount you owe.
CP504BYou have an unpaid amount due on your account. If you do not pay immediately, the IRS will levy certain property or rights to property to apply it to the amount you owe.
CP521A reminder that you have an installment agreement payment due.
CP523You have defaulted on your payment agreement. Therefore the IRS is terminating the agreement and will levy your assets.
CP601Usted tiene un saldo pendiente de pago (dinero que le debe al IRS) en una de sus cuentas contributivas.
CP603No hemos recibido respuesta de parte de usted y todavía tiene un saldo sin pagar en una de sus cuentas contributivas.
CP604Usted tiene un saldo sin pagar en su cuenta. De no pagar esta cantidad inmediatemente, el IRS embargará cualquier reembolso de impuestos estatales al que tenga derecho y aplicarlo al pago de su deuda.
CP604BUsted tiene un saldo sin pagar en su cuenta. De no pagar esta cantidad inmediatemente, el IRS embargará ciertas propiedades o derechos de propiedad y lo aplicará al pago de su deuda.
CP621Este aviso es para notificarle que usted tiene un plan de pagos a plazos vencido. Por favor, envíe el pago inmediatamente.
CP623Este aviso es para informarle nuestra intención de cancelar su plan de pagos a plazos y confiscar (embargar) sus bienes. Usted incumplió en su acuerdo.
CP711Nosotros realizamos cambios a su planilla debido a que entendemos que hubo un cálculo erróneo. Como resultado de estos cambios, usted adeuda dinero por sus contribuciones.
CP721Hicimos el(los) cambio(s) que usted solicitó a su declaración de impuestos para el año tributario que aparece en su aviso. Como resultado de éste(estos) cambio(s) usted debe dinero en sus impuestos.
CP722Hicimos el(los) cambio(s) que usted solicitó a su declaración de impuestos para el año tributario que aparece en su aviso. Como resultado de éste(estos) cambio(s) usted debe dinero en sus impuestos.
CP771Usted recibió este aviso para recordarle sobre la cantidad que adeuda en contribuciones, multas e intereses.
CP772Usted recibió este aviso para recordarle sobre la cantidad que adeuda en contribuciones, multas e intereses.
CP773Usted recibió este aviso para recordarle sobre la cantidad que adeuda en contribuciones, multas e intereses.
CP774Usted recibió este aviso para recordarle sobre la cantidad que adeuda en contribuciones, multas e intereses.
CP959Usted no radicó su planilla de contribución de negocios identificada en este aviso.
CP2000The income or payment information on file doesn’t match your tax return. The discrepancy may result in an increase or decrease in your tax due.
CP3219AThe IRS has received information that is different from what you reported on your tax return. This may result in an increase or decrease in your tax.
CP3219NThe IRS didn’t receive your tax return, so it calculated your return based on the information received from employers, financial institutions, and others. If you want to challenge the proposed tax, you have 90 days from the date of this notice. If you are outside the country, you have 150 days.
Letter 0012CThe IRS needs additional information to process your tax return.
Letter 0484CThe IRS wants a completed
Letter 0525Updates you on proposed changes after an IRS examination. Any changes are explained and details the refund due or taxes owed.
Letter 531IRS Notice of Deficiency. The information the IRS received about you was different from what you reported on your return.
Letter 0668D(LP 68)The IRS released their levy.
Letter 0549CYour tax bill was paid.
Letter 0681CThe IRS accepted your payment proposal. However, this is not a formal Installment Agreement.
Letter 0757CYou did not adhere to the terms of your Installment Agreement.
Letter LT 11The IRS plans to seize your property or rights to property.
Letter 1058The IRS has not received your payment. It plans to seize your property or rights to property.
Letter 1615 (LT 18)You must respond to the IRS within 10 days of this notice regarding past due tax returns.
Letter 1737 (LT 27)Complete and sign Form 433F, Collection Information Statement.
Letter 1961CYour application for a Direct Debit Installment Agreement was declined. It explains why and what you need to do to qualify.
Letter 1962CYour application for a
Letter 2050 (LT 16)The IRS is trying to collect unpaid taxes from you from returns that have been filed or from returns that have not been filed.
Letter 2257CThe IRS is providing the payoff amount that you requested.
Letter 226-JAn IRS letter to large employers notifying them that they may be liable for an Employer Shared Responsibility Payment (ESRP).
Letter 2271CA request for an Installment Agreement has been approved. It explains the fees and how to qualify for a Low Income Fee Reduction. The letter may also request missing information.
Letter 2272CAn IRS letter explaining why your request to pay the balance due in installments was declined.
Letter 2273CA confirmation letter of your request to pay the balance due in installments. It contained the amount to pay, fees charged, and where to send payment. Instructions on how to apply for the Low Income Fee Reduction included.
Letter 2318CA response to a request to pay taxes due to payroll deductions. It also explains the fees that are charged.
Letter 2357CThe IRS is admitting that it did not send you the balance due notices that it should have.
Letter 2603CThe IRS accepted your installment agreement. The IRS will file a Notice of Federal Tax Lien on your personal property.
Letter 2604CThe IRS has accepted your request for installment payments. This IRS letter provides the monthly payment, the address where to send it, and the fees charged. The letter also provides instructions on how to apply for the Low Income Fee Reduction.
Letter 2761CThe IRS is requesting your combat zone service dates to ensure that it provides you with the special provisions and protection of the combat zone deferment. Copies of military orders or other documentation to support your time served may be requested. Civilians working in support of the Armed Forces may be required to provide a Letter of Authorization or a letter from their employer.
Letter 2789CAn annual reminder notice, as required by law, of the balance due to the IRS. It explains that penalties and interest continue to accrue until the balance is fully paid.
Letter 2840CConfirms your Installment Agreement request and includes the payment amount and due date. This IRS letter explains the fees charged for paying monthly and explains how to apply for the Low Income Fee Reduction (if you qualify).
Letter 3030CProvides an explanation of the tax, penalty, and interest still due on your account.
Letter 3127CA confirmation of your request to make a change to your Installment Agreement. This IRS letter explains the fees for the change. Changes can be to the payment amount or due date, or it can include additional liabilities.
Letter 3174A reminder of taxes due after the IRS has sent a Notice of Intent to Levy.
Letter 3217CThe IRS has accepted your request to pay the balance in installments. This IRS letter provides your payment amount, the due date, and fees charged. The letter also provides instructions on applying for the Low Income Fee Reduction (if you qualify).
Letter 3228 (LT 39)A request to pay the balance due within 10 days using the envelope provided.
Letter 3500The IRS has received your documents, and it needs additional time to review them.
Letter 3572Your Federal Income Tax Return has been selected for examination. The IRS auditor requests that you call to schedule an audit appointment.
Letter 4883CThe IRS received your federal income tax return but needs more information to verify your identity in order to process your tax return accurately.
Letter 4903 (LT 26)You must file your tax returns immediately. The IRS has previously contacted you, but it did not receive a response.
Letter LP 47The IRS is trying to locate the person identified in the letter and is requesting that you provide their new address.
Letter LP 59The IRS has not received a response to the notice of levy it previously sent.
Audit Letter 2205The IRS manages audits either by mail or through an in-person interview to review your records. The interview may be at an IRS office (office audit) or the taxpayer’s home, place of business, or accountant’s office (field audit).
Letter 915You recently underwent an audit, and the IRS informs you that you now owe taxes.

Key takeaways

  • IRS Letter 3688 notifies taxpayers of a substantial understatement penalty for underreported income.
  • Respond promptly to avoid additional penalties and delayed processing of returns.
  • Carefully review your tax return and compare it with IRS findings to address discrepancies.
  • Seek professional assistance if needed to resolve the issue effectively.

Share this post:

Table of Contents