TaxingFYI
Interactive federal tax course

Learn where the tax number comes from.

Tax is taxing. It should not be mysterious. Build a 2025 federal estimate step by step, watch each dollar move through the calculation, and then use the same transparent model to explore your own numbers.

Start the free courseOpen Tax Lab
  • No account for free use
  • Plain-language math
  • IRS sources nearby

One model, three ways in

Follow a path, look up a rule, or test a number.

12 lessons · selected lessons free

Course

A guided sequence of predictions, explanations, and animated before-and-after calculations.

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14 public references

Concepts

Public definitions, formulas, examples, misconceptions, IRS sources, and related lessons.

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Free · no account

Tax Lab

The complete calculator as a private browser sandbox with every intermediate stage visible.

Open tax lab

The paid continuation

Turn understanding into a personal planning notebook.

Membership unlocks the full course and a private workspace where estimates can be named, branched, compared, revised, exported, and shared. An account exists for that paid workspace—not as a toll for using the free calculator.

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Paid workspace

  • Complete interactive course
  • Saved estimates and notes
  • Scenario branches and comparisons
  • Revision history
  • Bracket-headroom explorer
  • CSV, print, and private share links

Deliberately scoped

The calculator teaches a model; it does not prepare a return or decide what someone should do.

What it models

W-2 wages, selected investment income, net short- and long-term gains, taxable Roth conversions, the standard deduction, ordinary and preferential rates, scoped NIIT, and withholding.

What it leaves out

Credits, dependents, age/blind, senior, tip, overtime, and car-loan-interest deductions, itemizing, business and self-employment tax, AMT, loss carryovers, special-rate gains, state tax, penalties, and filing eligibility decisions.