A cash basis to accrual conversion requires three things: recording every dollar you’ve earned but not collected and every expense you’ve incurred but not paid as of the conversion date, filing IRS Form 3115 to get the method change approved, and calculating a Section 481(a) adjustment so no income or deduction gets skipped or double-counted in the transition. For tax years beginning in 2026, the IRS forces the switch on many businesses once their average annual gross receipts pass $32 million over the prior three years.1Internal Revenue Service. Rev. Proc. 2025-32 Below that line, you can still convert voluntarily, usually because lenders or investors want financial statements that reflect what the business actually earned and owes.
Who Has to Switch to Accrual
Three separate rules can force accrual accounting on a business, and any one of them is enough.
The Gross Receipts Test
Section 448 bars certain entities from using the cash method once they grow past a size threshold. For tax years beginning in 2026, that threshold is $32 million in average annual gross receipts over the three prior tax years.1Internal Revenue Service. Rev. Proc. 2025-32 The number is indexed for inflation; the 2025 figure was $31 million.2Internal Revenue Service. Rev. Proc. 2024-40
The rule reaches C corporations, partnerships with a C corporation as a partner, and tax shelters. S corporations and qualified personal service corporations (engineering, law, accounting, and consulting firms owned by their professionals) sit outside it and can keep using the cash method at any revenue level.3Office of the Law Revision Counsel. 26 U.S. Code 448 – Limitation on Use of Cash Method of Accounting
The Tax Shelter Rule
A business classified as a tax shelter must use accrual regardless of size. The definition is wider than most owners expect. Under Section 461(i)(3), it captures any non-C-corporation enterprise whose interests were offered in a registered securities offering, and any “syndicate” where more than 35 percent of losses flow to limited partners or others who don’t actively manage the business.4Office of the Law Revision Counsel. 26 U.S. Code 461 – General Rule for Taxable Year of Deduction Some real estate partnerships and investment funds land here without thinking of themselves as shelters. S corporations get a narrow carve-out: they’re not treated as tax shelters solely because they filed a notice of exemption from securities registration with a state.3Office of the Law Revision Counsel. 26 U.S. Code 448 – Limitation on Use of Cash Method of Accounting
The Inventory Rule
A separate rule requires accrual for purchases and sales whenever inventory is a material income-producing factor.5Internal Revenue Service. Rev. Proc. 2001-10 Retailers and manufacturers holding goods for resale fall squarely inside. But small businesses that pass the gross receipts test can treat inventory as non-incidental materials and supplies, which effectively removes the accrual requirement for inventory. Stay under $32 million in average gross receipts and you can generally keep cash-basis books even with stock on the shelves.
The Adjustments You Make on the Conversion Date
The mechanical work is finding every transaction that already happened economically but never showed up on your cash-basis books. Each item below moves your balance sheet, and most of them move taxable income. Together they produce the single number you’ll report on Form 3115.
Accounts Receivable
List every unpaid customer invoice open on the conversion date. Cash basis ignored these because no money had come in. Accrual makes them an asset and current-period revenue. If $200,000 is outstanding, income rises by $200,000. This is almost always the largest adjustment, and it’s the one that pushes the tax bill up.
Accounts Payable and Accrued Expenses
The mirror image. Record every bill you’ve received but haven’t paid: vendor invoices for supplies, utilities, and services delivered before the conversion date. They become liabilities and current-period deductions, which reduces taxable income.
Vendor bills aren’t the whole list. Accrued expenses also include wages employees have earned but you haven’t paid, the employer’s share of payroll taxes on those wages, accrued interest on loans, and benefits like unused paid time off. These are easy to miss because no invoice arrives in the mail, and missing them means you lose real deductions that would offset the receivables jump.
Prepaid Expenses
Under cash basis, a full-year insurance premium or a year of prepaid rent was deducted the day you wrote the check. Accrual treats that payment as an asset that expenses out over the coverage period. A $12,000 twelve-month insurance premium generates expense only for the months already elapsed; the rest sits as a prepaid asset. The conversion reverses the immediate cash-basis deduction and rebuilds the asset for the months still to come.
Deferred Revenue
If customers pay in advance for work you haven’t delivered, cash basis booked that as revenue on the day the payment cleared. Accrual says you haven’t earned it, so the cash sits as a liability called deferred revenue and turns into revenue only as you perform. This adjustment lowers taxable income at conversion because it reclassifies collected cash from earnings to obligation.
Inventory
If you carry inventory and don’t qualify for the small-taxpayer exception, you need a proper valuation at the conversion date. Purchases stop expensing as you pay for them and start capitalizing as an asset. Only the cost of goods actually sold flows through the income statement. Pick an acceptable costing method such as first-in, first-out and use it consistently going forward.
One item that doesn’t change: depreciation. It’s a non-cash allocation that works the same under both methods for tax purposes. If your schedules were right on cash basis, they carry over.
Filing Form 3115
You cannot just start using accrual. The IRS requires Form 3115, Application for Change in Accounting Method, for any method change, voluntary or mandatory.6Internal Revenue Service. Instructions for Form 3115 Skip it and the IRS doesn’t recognize the change; it can then impose whatever method it considers correct on terms you won’t like.
Automatic Consent Covers Most Conversions
The IRS runs method changes on two tracks. The automatic consent procedure covers most routine changes, including cash-to-accrual. If your change qualifies, you don’t request permission in advance and you don’t pay a user fee. You file Form 3115 with your return and the change takes effect. The current list of automatic-consent changes lives in Rev. Proc. 2025-23 and is updated periodically.6Internal Revenue Service. Instructions for Form 3115
Non-automatic changes require advance IRS approval, a user fee, and longer processing. Most cash-to-accrual filers won’t end up here, but unusual facts or audit-related changes sometimes push a filing onto that track.
How and When to File
Attach the original Form 3115 to your timely filed federal return (including extensions) for the year of the change, and send a signed duplicate to the IRS processing center in Ogden, Utah.7Internal Revenue Service. Where to File Form 3115 Missing either copy can invalidate the change.
The Audit Protection Payoff
Filing Form 3115 buys audit protection for earlier tax years. When the IRS grants a method change, it generally won’t reopen the same item on returns filed before the change. If you’ve been on the cash method when you shouldn’t have been, a properly filed Form 3115 keeps the fallout limited to the Section 481(a) adjustment instead of exposing every prior return.6Internal Revenue Service. Instructions for Form 3115 That alone makes proactive filing worth doing, even if you’re a year or two behind on the switch.
The Section 481(a) Adjustment and Your Tax Bill
Every conversion adjustment above collapses into one number, the Section 481(a) adjustment. Its job is to keep income and deductions from being permanently skipped or counted twice as you move between methods.8Office of the Law Revision Counsel. 26 U.S. Code 481 – Adjustments Required by Changes in Method of Accounting
The math: add the items that raise income under accrual (mostly accounts receivable) and subtract the items that lower it (accounts payable, accrued expenses, deferred revenue). Net them. A positive result means you owe tax on income earned but never reported on cash basis. A negative result gives you a deduction.
Positive Adjustments Spread Over Four Years
The IRS doesn’t require you to absorb a big positive adjustment in one year. Under Rev. Proc. 2015-13, a positive Section 481(a) adjustment is taken ratably over four tax years: the year of change and the three that follow.9Internal Revenue Service. Rev. Proc. 2015-13 A $400,000 net adjustment means $100,000 of extra income on each of the next four returns. The spread keeps the conversion itself from creating a crushing one-year bill.
Negative Adjustments Come Off in Year One
A negative adjustment is deducted in full in the year of the change.9Internal Revenue Service. Rev. Proc. 2015-13 Since a negative number means the IRS is returning deductions you missed, there’s no reason to delay them.
What Skipping Form 3115 Costs You
The four-year spread and the audit protection depend on filing Form 3115 proactively. If the IRS discovers the change should have happened and you never filed, it can impose the change on its own terms, including requiring the entire positive adjustment in a single year. Filing late on your own almost always beats letting the IRS catch it.
Timing Choices That Lower the Tax Hit
The conversion date isn’t arbitrary. A year-end when receivables are unusually low shrinks the positive 481(a) adjustment. A year-end where large vendor bills and accrued payroll are still open pushes up the negative side. If you have discretion over when to switch, look at what your balance sheet will hold on the candidate dates.
Clean the books before you calculate anything. The recurring problem in a cash-to-accrual conversion is bad source data: invoices never entered, vendor bills filed but not recorded, payroll accruals miscalculated. A messy cash-basis ledger becomes a messier accrual ledger. Get an accurate accounts receivable aging, a complete vendor ledger, and correct payroll accruals in place first, then run the Section 481(a) numbers.