Section 179 vs. bonus depreciation: what each election does on the return, and what neither one does to your books

Section 179 vs. bonus depreciation is a choice about the return, not about the books. Section 179 is elected item by item and capped twice, in dollars and by your business income. Bonus depreciation applies to a whole class of property unless you elect out, and carries no dollar cap. Neither one changes a single entry in your books.

That last sentence is the part almost nobody writes down, and it is the one that decides what happens on your side. The machine you just wrote off in full on the return is still sitting on your balance sheet on December 31, and your profit and loss statement will not show the deduction you just claimed.

This article assumes the purchase already became an asset. If you have not got that far, the question before this one is whether the cost had to be capitalized at all, and the de minimis safe harbor is where that gets decided.

Section 179 and bonus depreciation, compared on the axes that actually differ

Both let you deduct the cost of qualifying property in the year you place it in service instead of spreading it across years. They differ on how much, how you get it, how finely you can control it, and what happens to what is left over.

You will meet this provision under three names, which is part of why the topic reads as harder than it is. Publication 946 and Form 4562 call it the special depreciation allowance. The One, Big, Beautiful Bill guidance calls it the additional first year depreciation deduction. Everyone else calls it bonus depreciation. They are the same thing.

The granularity row is the one that does the most work in practice. Publication 946 puts the special depreciation allowance after any section 179 deduction and before regular MACRS depreciation, and the election out of bonus is made for a class of property rather than for one machine. So section 179 is the fine control and bonus is the blunt one, and that is a different distinction from which is bigger.

The income test is worth reading twice. Publication 946 limits the total section 179 cost you can deduct to your taxable income from the active conduct of a trade or business during the year, and says that any cost not deductible because of that limit can be carried to the next year and used to figure the following year's deduction. So a business that places $80,000 of machines in service in a year its taxable income from the business is $9,000 does not get an $80,000 section 179 deduction, and does not lose the other $71,000 either. The special depreciation allowance is figured a different way entirely, by multiplying the depreciable basis of the property by the applicable percentage.

What the 2026 numbers are, and what the One Big Beautiful Bill changed

For tax years beginning in 2026, the maximum section 179 expense deduction is $2,560,000, and that maximum is reduced by the amount by which the cost of section 179 property you place in service during the year exceeds $4,090,000. The section 179 cap for a sport utility vehicle placed in service in a tax year beginning in 2026 is $32,000. The IRS publishes all three figures with the rest of the 2026 inflation adjustments.

Bonus depreciation is where the ground moved. The One, Big, Beautiful Bill provides a permanent 100% additional first year depreciation deduction for qualified property acquired after January 19, 2025. Treasury and the IRS issued guidance on it in January 2026, as interim guidance ahead of proposed regulations. The same guidance gives taxpayers an election to deduct 40%, or 60% for certain property with longer production periods and certain aircraft, instead of the 100%, for qualified property placed in service during the first tax year ending after January 19, 2025.

Two words in there matter more than the number. Permanent means the schedule of declining percentages that ran through 2023, 2024 and 2025 stopped being the plan. The IRS states on its Working Families Tax Cuts page for businesses that the section 179 increases are permanent as well, and inflation adjusted for years beginning after 2025, which is where the 2026 figures above come from.

Acquired is the second one. The 100% rule keys off property acquired after January 19, 2025, and the section 179 limits key off property placed in service in the tax year. Those are two different dates on the same purchase, and they are both dates your books should be able to produce.

So if you are reading a page that gives bonus depreciation as 80%, or 60%, or 40% flat, check its date. Those were the percentages on the old step-down schedule, and a page written before January 2026 has no way of saying otherwise.

One $46,000 machine, carried through the return and through the books

Here is the whole article in one worked example. A fabrication shop buys a $46,000 machine and places it in service on October 1. In its books the shop depreciates equipment straight line over seven years. Every number here is an illustration, not a rule about what your own useful life should be.

On the return, with bonus depreciation at 100%, the shop deducts the full $46,000 in year one and the property's tax basis goes to zero.

In the books, nothing of the kind happens. The asset goes on the balance sheet at $46,000 and starts depreciating. Three months of a seven-year straight-line life is $1,643.

The bottom row is the point. Nothing was created and nothing was lost. The same $46,000 came off in both places, and the only thing that differs is when. That is what an accountant means by a timing difference, and it is why the write-off you claimed in October will not appear anywhere on the P&L you print in January.

Now run the same machine through section 179 instead. Say the shop elects out of the special depreciation allowance for that class of property, elects section 179 on the machine, and has $12,000 of taxable income from the active conduct of the business before the deduction. The deduction is limited to $12,000. The remaining $34,000 carries to next year and is used to figure next year's section 179 deduction.

The books do not move. Still $1,643 of depreciation expense in year one, still $44,357 on the balance sheet at December 31. The books do not know which election was made and they do not need to.

Why your profit and loss statement will not show the write-off

Your books depreciate the asset over its useful life because that is what the books are for. The SEC's Beginners' Guide to Financial Statements puts it plainly: companies spread the cost of long-lived assets over the periods they are used, and the charge for using an asset during a period is a fraction of its original cost. A machine that will run for seven years is a seven-year cost, and a set of books that dumped all of it into October would be telling you October lost money it did not lose.

The return is answering a different question, so it gets a different number. That is not a discrepancy anybody needs to fix. It is a book-tax difference, it is entirely ordinary, and the return has a name for it.

The clearest proof that it is expected is that the return has a line for it. A corporation filing Form 1120 completes Schedule M-1, which the IRS titles "Reconciliation of Income (Loss) per Books With Income per Return", and the first itemized line under expenses recorded on the books that were not deducted on the return is depreciation. Larger corporations file the more detailed Schedule M-3 instead. Either way, the form starts from what the books say and adjusts to what the return says, which only makes sense if the two were never supposed to match.

So when your depreciation schedule from your accountant and your fixed asset balance in QuickBooks disagree, the first question is not which one is wrong. It is which one you are looking at. One of them is tracking basis for the return and one of them is tracking carrying amount for the books, and in the year of a section 179 or bonus election they will be as far apart as they ever get. Checking the fixed asset line against the schedule behind it is one of the tie-outs on a balance sheet, and this is the year it looks wrong when it is not. Say which is which when the file goes to your accountant at year end, so the difference is explained before anyone has to ask.

This is the same lesson as the way a profitable month can leave less cash than it started with, arriving from the other direction. There, a profitable month had no money in it. Here, a deduction of $46,000 involves no additional money leaving the account in the year you claim it, and no expense on your income statement either.

What your asset record has to carry after the election

Publication 583 is short about this and it is the only place the bookkeeping consequence is stated as a requirement. The IRS says you must keep records to verify information about your business assets, because you need them to figure annual depreciation and the gain or loss when you sell. The records it lists should show when and how you acquired the asset, the purchase price, the cost of any improvements, the section 179 deduction taken, the deductions taken for depreciation, and how you used the asset.

Read the fourth and fifth of those again. Section 179 deduction taken and deductions taken for depreciation are two separate lines about the same asset. The IRS is not asking for one number. It is asking for both, because they are different numbers and the difference is the whole subject of this article.

Three things follow for the fixed asset register, and none of them are optional if you want the register to still be useful in year four.

1. Both dates, not one. Acquisition date and placed-in-service date are different fields and both are used. One decides eligibility for the 100% rule; the other decides which tax year the deduction lands in.

2. Both depreciation figures, side by side. The book figure and whatever came off on the return. A register carrying only one of them cannot answer a question about the other, and the year the asset is sold is the year somebody asks.

3. The invoice, kept with the asset and not just with the month. The purchase price and the cost of any improvements are both in the list above, and improvements arrive years after the original invoice has been filed away.

None of that is exotic and all of it is the kind of thing that quietly stops being true when nobody is keeping the register current every month. An asset log is only worth what its oldest row is worth.

Recapture is the reason the asset record has to outlive the deduction rather than a reason to worry about taking one. If business use of the property drops to 50% or less after a section 179 deduction, the recapture amount is ordinary income reported in Part IV of Form 4797, and the property's basis increases by that amount. Computing it needs the original cost, the business-use percentage in the year you placed it in service, and the deduction taken. If those three are in the register, it is arithmetic. If they are not, it is archaeology.

Placed in service, not paid for

The date that decides which tax year a deduction lands in is the date the property is placed in service. Publication 946 defines it: property is placed in service when it is ready and available for use in your business, even if you have not begun using it. The definition reaches idle property, which is exactly the case that catches people out in the last week of December.

Not the order date. Not the invoice date. Not the date the finance company drew the first payment.

Take a machine ordered on December 12, delivered on December 28, and uncrated, wired in and commissioned on January 4. It was paid for in December and it belongs to the next tax year. Take the same machine delivered December 22 and sitting ready on the shop floor on December 29 with nobody scheduled to run it until January. Ready and available is the test, so it is in the earlier year.

This is where the bookkeeping and the tax question stop being separable, because only one set of records knows which of those two happened.

A register that records only the invoice date has thrown away the field that decides the answer. It is a two-minute job in the month a machine arrives and an unanswerable question fourteen months later.

Whether either election is worth making on your own return depends on your entity, your income this year against next year, and whether your state follows the federal rules at all. That is a conversation with whoever files your return, and it is worth having before December rather than in April, because by April the placed-in-service date is already whatever your records say it is.

Is bonus depreciation still 100% in 2026?

Yes. The One, Big, Beautiful Bill provides a permanent 100% additional first year depreciation deduction for qualified property acquired after January 19, 2025, and Treasury and the IRS published guidance on it in January 2026. "Permanent" is the change: the earlier schedule stepped the percentage down year by year, and that schedule no longer governs property acquired after that date.

There is an election to take less. For qualified property placed in service during the first tax year ending after January 19, 2025, a taxpayer may elect to deduct 40%, or 60% for certain property with longer production periods and certain aircraft, instead of the 100%.

Separately, and for any year, you can elect not to claim the special depreciation allowance at all for a class of property. That election is made by attaching a statement to a timely filed return, including extensions, saying you are electing out and naming the class.

Can I take Section 179 on a financed purchase?

The test is when the property is placed in service, not when it is paid for. Publication 946 gives the section 179 deduction in the year the qualifying property is placed in service, and defines placed in service as ready and available for use in your business. Payment terms are not part of that definition.

That is why the deduction and the cash rarely line up. Financing a $46,000 machine means the deduction can be claimed in full in year one while the payments run for five years, and the reverse is also true: paying cash in December for equipment that will not be ready until February does not move the deduction into December.

Your books handle the two halves separately, and they should. The asset goes on the balance sheet at cost. The loan goes on as a liability. The payments split between principal, which reduces the liability, and interest, which is an expense. None of those three entries changes because of a section 179 election.

What is the Section 179 limit for 2026?

For tax years beginning in 2026, the maximum section 179 expense deduction is $2,560,000. That maximum is reduced, dollar for dollar, by the amount by which the cost of section 179 property you place in service during the tax year exceeds $4,090,000. The maximum section 179 expense deduction for a sport utility vehicle placed in service in a tax year beginning in 2026 is $32,000.

A second limit sits behind the dollar one and catches far more small businesses than the phase-out ever will. The total cost you can deduct under section 179 is limited to your taxable income from the active conduct of a trade or business during the year. Any cost disallowed by that limit carries to the next year and is used to figure that year's section 179 deduction. Form 4562 walks the arithmetic in Part I: the carryover in from last year, the business income limitation, the deduction capped at it, and the carryover out to next year each get their own line.

Does Section 179 change my profit and loss statement?

No. A section 179 election is made on Form 4562 as part of your tax return, and it changes what the return deducts. Your profit and loss statement shows book depreciation, which spreads the asset's cost over the periods it is used, and it carries on doing that for the asset's whole useful life regardless of what the return did in year one.

The result is that the two numbers disagree, on purpose, for years. A $46,000 machine written off in full on the return might show $1,643 of depreciation expense on the P&L in the same year, and $6,571 a year after that. Corporate returns reconcile the difference on Schedule M-1, "Reconciliation of Income (Loss) per Books With Income per Return", where depreciation is an itemized line.

If you want the deduction reflected in a figure you can see on your own reports, the place it shows up is the tax provision or the tax bill itself, not the operating lines above it. On a sole proprietor's return, both elections land together on the Schedule C line captioned for depreciation and the section 179 expense deduction, and knowing which line each account in your books maps to is worth doing before the difference surprises you.

Which vehicles qualify for Section 179?

Vehicles are listed property, which is a category with its own rules on top of everything else. The controlling test is use: you can elect the section 179 deduction only if you use the property more than 50% for business in the year you place it in service, and where business use is above 50% you multiply the cost by the business-use percentage to get the business cost the deduction is figured on. Property not used predominantly for qualified business use in the year it is placed in service does not qualify for the section 179 deduction, and does not qualify for a special depreciation allowance either.

Above that sit two separate caps. Passenger automobiles have their own depreciation limits. A four-wheeled vehicle primarily designed or used to carry passengers on public roads that is not subject to those passenger automobile limits and is rated at no more than 14,000 pounds gross vehicle weight is the sport utility vehicle class, and its section 179 cap is $32,000 for vehicles placed in service in tax years beginning in 2026.

The bookkeeping consequence is a mileage log, because the business-use percentage is not an estimate you make in April. It is a measurement taken across the year, it decides the size of the deduction, and it is the number recapture is later computed against if business use falls.