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Unit 6: Finishing the Return

Master tax liability, marginal rates, AMT, NIIT, Form 2210, extensions, amended returns, and decedents for 2026.

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Shmuel Eagle

Shmuel Eagle

Instructor

Unit 6: Finishing the Return

What Will You Learn

  • Calculate federal income tax using 2026 progressive marginal rate brackets
  • Explain the difference between marginal and effective tax rates to clients
  • Adjust Form W-4 withholdings to eliminate large refunds or tax due surprises
  • Determine Alternative Minimum Tax liability and exemption phase-outs on 6251
  • Apply the 3.8% Net Investment Income Tax on Form 8960 for high-income filers
  • Prevent underpayment penalties using 90%/100%/110% safe harbor benchmarks
  • Prepare Form 4868 filing extensions and advise clients on tax payment deadlines
  • Prepare amended returns on Form 1040-X within the 3-year statutory window
  • Navigate the 3-year Refund Statute Expiration Date for prior-year returns
  • Prepare final returns for deceased taxpayers and claim refunds on Form 1310

About This Class

Course & Unit Overview: Finishing & Filing the Return (Classes 21–22)

Welcome to Unit 6 of BlueLink Academy’s 1040 Income Tax Preparation Course. This unit covers the final tax calculation, Alternative Minimum Tax (AMT), Net Investment Income Tax (NIIT), underpayment penalties on Form 2210, filing extensions on Form 4868, amended returns on Form 1040-X, deceased taxpayer returns, and special non-resident filing situations.

The Preparer's Mindset

Filing a tax return is an exact legal submission. An extension of time to file is never an extension of time to pay. A professional preparer guides clients through tax liabilities calmly, sets up appropriate quarterly withholding, and ensures flawless e-file execution.

Unit Curriculum Architecture

Class 21

Tax Liability, AMT, NIIT & Penalties

Progressive brackets, W-4 withholding strategy, Form 6251 AMT, Form 8960 NIIT, and Form 2210 underpayment penalties.

Class 22

Extensions, Amended & Special Returns

Form 4868 extensions to October 15, Form 1040-X amendments, 3-year RSED refund rule, deceased returns, and Form 1040-NR basics.

Unit Quick Reference Table

Filing Procedure / Tax Rule IRS Form 2026 Statutory Deadline / Rate
Automatic Filing Extension Form 4868 6-month extension to October 15 (Extension to FILE, not to PAY)
Late Filing Penalty IRC §6651(a)(1) 5% per month of unpaid tax up to 25% maximum
Late Payment Penalty IRC §6651(a)(2) 0.5% per month of unpaid tax up to 25% maximum
Amended Individual Return Form 1040-X 3 years from filing date or 2 years from tax payment date
Net Investment Income Tax Form 8960 3.8% surtax over $200k Single / $250k MFJ MAGI thresholds
Requirements
  • Completion of Units 1 through 5 of the 1040 Preparation Program
  • Firm grasp of filing status, gross income, AGI, deductions, and credits
  • Access to a financial calculator, spreadsheet, or tax prep software
  • Reference to 2026 tax brackets, AMT thresholds, and Form 2210 rules
  • Adherence to IRS Circular 230 standards and client confidentiality

Frequently Asked Questions

What is the difference between a marginal tax rate and an effective tax rate?
A taxpayer's marginal rate is the tax bracket applied to their last dollar of taxable income. The effective tax rate is the overall percentage of total income actually paid in taxes (total tax divided by total income). Because the U.S. tax system is progressive, moving into a higher tax bracket only taxes the dollars within that specific bracket at the higher rate, never the taxpayer's entire income.
Why is getting a massive tax refund often a sign of poor tax planning?
A large refund simply means the client overpaid taxes throughout the year via excessive wage withholding, essentially giving the government an interest-free loan. Proper planning with Form W-4 allows the client to keep that money in their monthly budget or emergency fund while aiming for a balanced result (close to $0 refund or balance due).
Who is subject to the Alternative Minimum Tax (AMT) for 2026?
The AMT is a parallel tax system designed to ensure high earners pay a minimum level of tax by adding back certain deductions. Under the One Big Beautiful Bill Act (OBBBA), generous exemption amounts ($90,100 Single / $140,200 MFJ for 2026) protect most middle-class taxpayers, but high earners with significant state taxes, incentive stock options (ISOs), or private activity bond interest must calculate AMT on Form 6251.
What triggers the 3.8% Net Investment Income Tax (NIIT) on Form 8960?
The NIIT applies to individuals with Modified Adjusted Gross Income (MAGI) exceeding statutory thresholds: $200,000 for Single/Head of Household or $250,000 for Married Filing Jointly. The 3.8% tax applies to the lesser of net investment income (interest, dividends, capital gains, rental income) or the amount by which MAGI exceeds the threshold.
What safe harbor rules protect clients from the underpayment of estimated tax penalty?
Taxpayers generally avoid the underpayment penalty if their withholding and estimated payments equal at least: (1) 90% of current-year tax liability, OR (2) 100% of prior-year tax liability (increased to 110% if prior-year AGI exceeded $150,000). Wage earners can adjust Form W-4 late in the year to catch up because withholding is treated as paid evenly throughout the year.
Does filing an extension on Form 4868 give the client extra time to pay taxes owed?
No. Form 4868 provides an automatic 6-month extension of time to FILE the return (until October 15), but it does NOT extend the time to PAY. Any tax owed must be estimated and paid by the original April deadline. Unpaid balances immediately begin accruing interest and failure-to-pay penalties.
How do the IRS failure-to-file and failure-to-pay penalties compare?
The failure-to-file penalty is much harsher: 5% of unpaid tax per month (up to 25%). The failure-to-pay penalty is 0.5% per month (up to 25%). Therefore, clients who cannot afford to pay should always file on time (or request an extension) to avoid the severe 5% monthly late filing penalty, and arrange an installment agreement for the balance.
How far back can a taxpayer claim a refund on an amended return (Form 1040-X)?
Under the Refund Statute Expiration Date (RSED), a taxpayer must file Form 1040-X within 3 years from the date the original return was filed (or 3 years from the original April due date if filed early), or within 2 years from the date the tax was paid, whichever is later. Returns filed after this window forfeit any refund permanently to the U.S. Treasury.
What rules apply when filing a final return for a deceased taxpayer?
The final return covers income earned up to the date of death. The surviving spouse can file Married Filing Jointly for the full year of death if not remarried, writing "deceased," the date of death, and signing on behalf of the decedent. If there is no surviving spouse, the court-appointed personal representative signs; if a refund is due and no representative was appointed, Form 1310 must be attached.
When should a tax preparer refer out a non-resident or dual-status alien return?
Non-resident alien returns (Form 1040-NR) and dual-status returns involve complex international tax treaties, residency starting/ending rules, and foreign tax credit mechanics. Preparers without specialized training in international taxation should recognize the limits of their practice and refer these clients to an international tax specialist to prevent costly reporting errors.

Meet Your Instructors

Shmuel Eagle

Shmuel Eagle

Lead Tax Instructor

Co-founder of BlueLink with 15+ years in tax preparation and office management.

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