To calculate declining balance depreciation, multiply the asset’s remaining book value at the start of each year by a fixed rate, where the rate equals the declining balance percentage (200% or 150% under MACRS) divided by the asset’s recovery period in years. The first year uses a timing convention that reduces the deduction, and at the point where straight-line would produce a larger deduction than the declining balance formula, tax rules require you to switch. That is how to calculate declining balance depreciation from start to finish, and the sections below walk through each piece with a worked example.
Inputs You Need Before You Start
Three numbers drive every calculation: cost basis, recovery period, and the declining balance rate.
Cost basis is the full amount invested in the asset. Include the purchase price, sales tax, shipping, and installation costs.1Internal Revenue Service. Publication 551 – Basis of Assets Trade-in value and payments made in services also count. Every year’s depreciation flows from this number, so getting it right matters.
Recovery period is the number of years over which you spread the deductions. Under MACRS, you don’t estimate useful life yourself. The IRS assigns each type of property to a class with a fixed recovery period.2Internal Revenue Service. Publication 946 – How To Depreciate Property Common classes:
- 5-year property: cars, trucks, computers, office machinery, and research equipment
- 7-year property: office furniture, fixtures, safes, and most assets that don’t fit another class
- 10-year property: vessels, barges, and single-purpose agricultural structures
- 15-year property: land improvements like fences, roads, sidewalks, and shrubbery
- 20-year property: farm buildings and municipal sewers
Salvage value is a special case. It matters for book depreciation under generally accepted accounting principles, where it acts as a floor. For tax purposes under MACRS, salvage value is disregarded and the percentage tables depreciate the full basis down to zero. If you’re calculating for a tax return, you can ignore it. If you also prepare financial statements for lenders or investors, track it separately.
The Rate and the Annual Formula
The depreciation rate is the declining balance percentage divided by the recovery period. For 200% declining balance on 5-year property, that’s 200% ÷ 5 = 40%. For 150% declining balance on 15-year property, it’s 150% ÷ 15 = 10%.2Internal Revenue Service. Publication 946 – How To Depreciate Property
Which percentage applies depends on the property class. Most tangible personal property used in a non-farming business (3-, 5-, 7-, and 10-year classes) uses 200% declining balance by default. Property in the 15-year and 20-year classes uses 150% declining balance. Farm equipment placed in service after 2017 also qualifies for 200%.2Internal Revenue Service. Publication 946 – How To Depreciate Property You can elect the 150% rate for property that would otherwise get 200%, or elect straight-line, if you prefer smoother deductions.3Office of the Law Revision Counsel. 26 U.S. Code 168 – Accelerated Cost Recovery System Once elected for a property class, the choice binds every asset in that class placed in service the same year.
The rate stays fixed. What changes each year is the number the rate multiplies. Year one applies the rate (adjusted for the timing convention) to the full cost basis. Every year after, the rate applies to remaining book value, which is cost basis minus all depreciation already claimed. Because book value shrinks, the annual dollar amount shrinks with it.
A Worked Example
Suppose you buy $10,000 of computer equipment. Computers are 5-year MACRS property, so the default is 200% declining balance with the half-year convention. The rate is 40%.
The half-year convention treats the asset as placed in service on July 1, so the first year gets only half the normal deduction:4eCFR. 26 CFR 1.168(d)-1 – Applicable Conventions – Half-Year and Mid-Quarter Conventions
- Year 1: $10,000 × 40% × 50% = $2,000. Book value drops to $8,000.
- Year 2: $8,000 × 40% = $3,200. Book value drops to $4,800.
- Year 3: $4,800 × 40% = $1,920. Book value drops to $2,880.
- Year 4: Switch to straight-line = $1,152. Book value drops to $1,728.
- Year 5: Straight-line = $1,152. Book value drops to $576.
- Year 6: Straight-line for the remaining half-year = $576. Book value reaches $0.
The recovery period is five years, but the half-year convention stretches the deductions across six tax years. The largest deduction lands in year two, not year one, because year one is cut in half. Total depreciation equals the full $10,000 basis.
When to Switch to Straight-Line
MACRS doesn’t allow declining balance all the way to zero. The formula produces smaller deductions each year, and at some point straight-line catches up. When it does, you must switch.2Internal Revenue Service. Publication 946 – How To Depreciate Property
Each year, compare two numbers: the declining balance deduction (book value × rate) and the straight-line deduction (book value ÷ remaining years in the recovery period). Use the larger one. In the example above, year 4 is the crossover. The declining balance figure would be $2,880 × 40% = $1,152, and straight-line gives $2,880 ÷ 2.5 = $1,152. Equal, so you switch. From that point the deduction stays level because straight-line spreads the remaining book value evenly.
You don’t have to run this comparison yourself. IRS Publication 946 includes MACRS percentage tables in Appendix A that already fold in the switch, the half-year convention, and the correct rate for each class.2Internal Revenue Service. Publication 946 – How To Depreciate Property For 5-year property under 200% declining balance with the half-year convention, the annual percentages applied to the original cost are 20.00%, 32.00%, 19.20%, 11.52%, 11.52%, and 5.76%. Multiply the original cost by each percentage and the calculation is done.
Half-Year vs. Mid-Quarter Convention
The timing convention determines how much you claim in the first and final years. Two conventions apply to personal property under MACRS.
The half-year convention is the default. Every asset is treated as placed in service on July 1 regardless of the actual date, giving half a year of depreciation in the first year and half in the final year.4eCFR. 26 CFR 1.168(d)-1 – Applicable Conventions – Half-Year and Mid-Quarter Conventions
The mid-quarter convention takes over when more than 40% of the total cost of property placed in service during the year was placed in service in the last three months. The rule prevents businesses from stacking purchases in December and claiming half a year of depreciation for a few weeks of ownership. Under mid-quarter, each asset is treated as placed in service at the midpoint of the quarter it was actually acquired.4eCFR. 26 CFR 1.168(d)-1 – Applicable Conventions – Half-Year and Mid-Quarter Conventions An asset acquired in October gets about a month and a half of depreciation instead of six months.
Run the 40% test before committing to major fourth-quarter purchases. Tripping mid-quarter reduces the first-year deduction on every asset placed in service that year, not just the ones bought late.
Which Property Can’t Use the Declining Balance Method
Some property is excluded from accelerated depreciation entirely. The tax code requires straight-line for nonresidential real property (commercial buildings), residential rental property, and railroad grading or tunnel bores.3Office of the Law Revision Counsel. 26 U.S. Code 168 – Accelerated Cost Recovery System Land is never depreciable. Intangibles, films, and recordings are outside MACRS altogether.2Internal Revenue Service. Publication 946 – How To Depreciate Property If the assets in question are buildings or apartments, the declining balance method isn’t on the table.
Reporting the Deduction on Form 4562
Depreciation is reported on Form 4562, Depreciation and Amortization. You must file this form whenever you place new depreciable property in service during the year, claim a Section 179 deduction, or report depreciation on vehicles or other listed property.5Internal Revenue Service. Instructions for Form 4562 Part III covers MACRS depreciation, where each asset’s recovery period, method, convention, and current-year deduction is listed.
For assets placed in service in prior years, a single line usually captures the total depreciation continuing from earlier returns. New assets get individual lines showing the month and year placed in service, the cost basis, and the method chosen. Vehicles and other listed property require additional detail in Part V, including the percentage of business use.
Keep records supporting every deduction for as long as they’re relevant to a return. That means purchase invoices, depreciation schedules showing each year’s calculation, and documentation of business-use percentages for listed property.6Internal Revenue Service. Publication 583 – Starting a Business and Keeping Records Missing records can lead to deductions being disallowed on examination, with back taxes and interest added.