Maintenance
Part of Federal business tax obligations and filing basics
Federal business tax rules: the sections behind a return
The federal business tax rules that govern a return, by name: IRC sections, Treasury regulations, the IRS forms they land on, and how to check the year.
A rule you read on a blog in March may have been changed in December. It may have been superseded in January, or it may never have been a rule.
This page names the federal business tax rules that apply to a business return, the forms they land on, and where the current text lives. It also shows how to check which year and taxpayer a rule covers before you rely on it.
What to take away
- Federal tax rules come in layersthe statute Congress writes, the regulations Treasury issues, the guidance the IRS publishes, and the forms and instructions you actually fill in. They do not change at the same speed.
- Many figures change every year by design. The number you remember is the number for the year you remember it from.
- An IRS page carries its own year, its own scope, and its own "what's new" section. Read those three before the body.
- No figure on this site is current by definition. The IRS page for your filing year is, and a CPA or enrolled agent decides how it applies to you.
The federal business tax rules that govern a return
A business return is not filed under one rule. It rests on a small set of named federal business tax rules:
- Internal Revenue Code §61 defines gross income.
- IRC §162 allows ordinary and necessary business expenses.
- IRC §167 and §168 govern depreciation and the Modified Accelerated Cost Recovery System (MACRS). Section 168(k) adds a special first-year depreciation allowance for qualified property in the year it is placed in service.
- IRC §179 allows expensing of qualifying property, within annual limits.
- IRC §199A provides the qualified business income deduction for pass-through entities.
- IRC §163(j) limits the deduction for business interest. Interest disallowed in one year is carried forward to the next, and for a partnership the limit is applied at the partnership level.
- IRC §469 limits passive activity losses and credits. A passive activity is a trade or business in which the taxpayer does not materially participate, and it includes any rental activity; a disallowed loss carries to the next taxable year.
- IRC §274 limits meals and entertainment deductions.
- IRC §280A limits home-office deductions.
- IRC §1401 and §1402 impose self-employment tax.
- Treasury Regulations carry the detailsTreas. Reg. §1.162-1 for business expenses, Treas. Reg. §1.167(a)-1 for depreciation, and the regulations under §274 for meal and entertainment substantiation. Treas. Reg. §301.7701-3 governs entity classification: an eligible entity with at least two members can elect to be classified as a corporation or a partnership, a single-owner entity can elect corporate status or be disregarded, and an entity that makes no election takes a default classification.
- Annual IRS revenue procedures and notices set the standard mileage rate and many inflation-adjusted limits.
The forms follow from the entity:
- Sole proprietorSchedule C (Form 1040) and Schedule SE (Form 1040).
- PartnershipForm 1065, with Schedule K-1 for partners.
- S corporationForm 1120-S, with Schedule K-1 for shareholders.
- C corporationForm 1120.
- EmployerForm 941, Form 940, and Form W-2 for employees.
The IRS publishes the text of these rules on its tax code, regulations and official guidance page. Publication 334, Tax Guide for Small Business, explains them for small businesses; Publication 535 covers business expenses; Publication 463 covers travel, gifts, and car expenses.
Each rule carries its own effective date. The IRS publication for your filing year has a "What's New" section that lists the changes for that year and a "Reminders" section that points out expired provisions. Read those before the body of the publication. The dollar limits and the standard mileage rate for the year are set by annual revenue procedures and notices, so use the IRS page for your filing year rather than a figure from memory.
Four layers, four speeds
| Layer | Who writes it | How it changes | What it looks like |
|---|---|---|---|
| The statute | Congress | An act is passed and signed. Changes can take effect at once, later, or for years already ended | Section numbers, dense text, the source everything below interprets |
| Regulations | The Treasury and the IRS, after public comment | Proposed, then final, sometimes temporary. Can take years | Long numbered documents explaining how a section is applied |
| Published guidance | The IRS | Rulings, procedures, notices and announcements appear in the Internal Revenue Bulletin | Shorter, dated, often the first place a year's figures appear |
| Forms, instructions and publications | The IRS | Reissued each year | The thing you fill in, with a year printed on the cover |
You do not need to know all four exist in order to file. You need to know which layer a claim came from. A post that says "the rule is X" usually summarizes the bottom layer, one or two years late.
Four layers of tax rules
Statute
- Who writes it
- Congress
- How it changes
- Act signed
- What it looks like
- Section numbers
Regulations
- Who writes it
- Treasury and IRS
- How it changes
- Proposed then final
- What it looks like
- Numbered documents
Published guidance
- Who writes it
- IRS
- How it changes
- Rulings and notices
- What it looks like
- Dated bulletin items
Forms
- Who writes it
- IRS
- How it changes
- Reissued yearly
- What it looks like
- Year on cover
The IRS describes how the layers rank on its page on the tax code, regulations and official guidance. Send that page to anyone who insists a summary is the law.
What changes every year and what does not
- Figures that are adjusted on a schedule. Many limits, thresholds and the standard mileage figure are reset by announcement. The figure for one year is not the figure for the next, which is why the mileage rates page on this site sends you to the IRS rather than printing a number.
- Provisions with an end date written in. Watch for phrases like "for tax years beginning before". A rule can be real and still be gone.
- Structural ruleswhat counts as income, what an ordinary and necessary expense is, how an entity is classified. These change rarely, by statute or regulation, and never by press release.
- Forms. Line numbers move. A guide that says "enter it on line 12" was right once.
How to read an IRS page
- Find the year. Publications say which year's returns they are for. A page you open this year may describe last year's return. Decide which year you are filing before you read further.
- Find the scope line. Most pages say who they apply tosole proprietors, partnerships, corporations, employers. If your entity is not in the list, the page is not about you.
- Read "What's New" before the body. It is short and it is where the changes are.
- Read "Reminders". This is where expired provisions are pointed out.
- Note the "page last reviewed or updated" line at the foot. It tells you the page's age, not the rule's.
- Follow the link to the form instructions. A publication explains; the instructions govern how the form is completed.
- When two IRS pages seem to disagree, stop. That is a question for a professional with both pages in front of them, not something to settle by picking the friendlier one.
Reading a rule against your own return
Every rule has a subject. Before you apply one, ask four questions.
Does this rule apply to me?
Does it apply to my entity?
check entity type first
the rule is not yours
Does it apply to my entity? The same expense is handled differently depending on whether the business is a sole proprietorship, a partnership or a corporation, which is why entity tax treatment comes before the rule, not after it.
Does it apply to my year? A rule can be right and still be the wrong year's.
Is it a rule or a figure? A rule about what makes an expense deductible can be learned once and carried. A figure has to be looked up each time. The business deductions overview draws that line for the common categories.
Does my state follow it? States adopt federal changes late, partly, or not at all. A federal rule tells you nothing certain about the state return.
Where the current text lives
Source / Use it for
- Internal Revenue Bulletin
- New guidance as it is published, with a date on it
- IRS forms and instructions page
- The current year's forms and the instructions that govern them
- Publication 334, Tax Guide for Small Business
- The plain-language overview for the year named on its cover
- The IRS newsroom
- Announcements of annual figures and of changes between publications
- A CPA or enrolled agent
- Whether any of it applies to your facts, and how
Of those, the one to read first is Publication 334, which is the IRS explaining its own rules to small businesses in ordinary sentences. Check the year on the cover, then stay inside what it says.
The federal business tax overview on this site describes the shape of the system. The IRS page for your filing year describes the rule. Only one of those is current by definition, and it is not the one you are reading now.
Common questions
A guide I trust says the rule is X. Is it?
Find the year on the guide. Find the IRS page for the year you are filing. Compare. If they disagree, the guide is out of date or was never right, and the IRS page wins either way.
Do I need to read regulations?
No. You need to know they exist, so that when your preparer cites one you understand it outranks anything you read on a forum.
How do I know when something changed?
The "What's New" section of the publication for your year, the IRS newsroom, and your preparer's annual letter. Not memory, and not last year's return.
The rule changed after I filed. Do I redo the return?
Some changes reach back into years already filed; most do not. That is a question for a professional with the specific change in front of them, and one of the tax deadlines that matters is the window for amending, so ask promptly rather than in a year's time.
