Bank Statement Loan Income Formula: 12 vs. 24 Months of Deposits

The Quick Read: Twelve months of deposits usually fits a borrower whose income is steady or rising, while 24 months fits one whose revenue swings from quarter to quarter. The formula itself does not change between the two. You total the eligible deposits, apply any expense factor, multiply by ownership share, and divide by the months in the window.

• The window changes the divisor and which deposits enter the average.
• Twelve months captures a recent run rate; 24 months smooths lumpy income.
• Transfers, loan proceeds, and unexplained large deposits are stripped out first.
• Business statements usually take an expense factor; personal statements usually take little or none.
• Qualifying income feeds your personal debt-to-income ratio, so the window can change buying power.

Here is the honest answer on who each option is for. Twelve months suits the self-employed borrower who had a strong recent year and wants that year to count. Twenty-four months suits the borrower with seasonal or lumpy deposits who wants one outlier quarter to matter less. Most programs Lendmire places files with are built around a 12-month window, and a longer one is a choice on certain programs, not a default. The best window is the one that produces the stronger, cleaner number for your actual deposits.

Side-by-Side

The table below shows published industry norms for both windows. Specifics vary by program sheet and lender, subject to lender guidelines.

How the Formula Works, Step by Step

Start with the statement type. A borrower can submit personal or business account statements, and the type drives how much of the deposit total survives.

1. Choose personal or business statements. Business statements generally take an expense-factor reduction. Personal statements generally count eligible deposits with little or no reduction, though a lender may ask where business expenses were paid.

2. Total the deposits across the full window, 12 or 24 consecutive months.

3. Remove non-income credits. Transfers between your own accounts, loan proceeds, refunds, and unsourced large deposits come out.

4. Apply the expense factor to business accounts. It is typically a program default, or a lower figure supported by a CPA letter or profit-and-loss statement. Lenders set their own factors, so no single percentage applies everywhere.

5. Multiply by your ownership share. A 60% owner counts 60% of the result.

6. Divide by the months in the window. That gives qualifying monthly income.

7. Run debt-to-income against your personal debts using that income.

The order matters. Clean the deposits first, then apply the expense factor, then prorate ownership, then divide. Dividing by the wrong number of months, or applying the expense factor twice, are the two most common self-inflicted errors.

The deposit-cleaning step is not a lender quirk. Under the federal ability-to-repay rule, CFPB Regulation Z requires a creditor to verify the income it relies on using reliable third-party records, and it does not prescribe a lookback length. The eCFR text of that rule lists financial institution records among acceptable sources, which is why bank statements work. The 12-versus-24 choice comes from program guidelines, not from law.

Key Terms Defined

Eligible deposit: A credit that reflects real business or personal earnings, not a transfer or loan.

Expense factor: The percentage of business deposits treated as operating cost before income is counted.

Lookback window: The number of consecutive months of statements the lender averages.

Qualifying income: The monthly figure left after exclusions, expense factor, ownership share, and averaging.

Ownership share: Your percentage of the business, used to scale the income you may count.

When 12 Months Is the Better Fit

Twelve months is the better fit when your latest year is your strongest. A shorter average lets recent growth carry the file instead of being diluted by a slower earlier year.

Picture a consultant whose second year of self-employment ran well above the first. A 24-month average blends the soft start into the number and understates today’s earnings. The 12-month window reflects the run rate a lender can actually see.

It also helps when you have limited history. Across most programs in Lendmire’s wholesale network, 12 months is the typical documentation period, so you are working with the common path. The tradeoff is real, though. A single unusually strong stretch can flatter the average, and a lender may look harder at whether that level is repeatable.

Twelve months also means less paper. Fewer statements mean fewer missing pages and fewer unexplained deposits to chase, and those are the usual file problems.

When 24 Months Is the Better Fit

Twenty-four months is the better fit when income is seasonal, lumpy, or has a large older peak. Two years of deposits spread an outlier across more months, so no single quarter decides the result.

Say you run a landscaping business with heavy summer deposits and thin winters. A 12-month window can land on an unlucky or lucky stretch depending on where it starts. Twenty-four months evens that out. It can also win when income is declining, because an older peak lifts the average above what the latest year alone would show.

Here is the catch. The 24-month average lags a rapidly rising income, and it requires two clean years of statements. Not every program offers the longer window, and one that does may price or structure the file differently. If your deposits are messy, two years of messy is more to explain, not less.

The practical move is to compute both averages on your own deposits, apply the same expense step to each, and compare. Then ask the broker to see which window the matching program will actually accept. The stronger number only helps if a program takes it.

Edge Cases That Move the Number

• Commingled accounts. Personal accounts that mix business and personal activity get extra review, with requests to identify deposits.
• Partial ownership. Income is typically scaled by your share. Business funds used for down payment or reserves may also be discounted.
• Unsourced large deposits. These can be excluded entirely. The CFPB’s official interpretations say funds flowing into an account do not meet the verification standard unless they are confirmed as income.
• Self-employment tenure. Many programs want around two years of history, though some accept one year with prior experience in the same field. Programs vary.
• Shorter windows. Some programs offer them for specific situations, but treat those as exceptions to confirm on the program sheet.

Leverage and Occupancy: What the Income Number Buys

Qualifying income matters because it sets your debt-to-income ratio and, with it, your buying power. Across the wholesale network, a primary residence on bank-statement documentation reaches up to 90% LTV on a purchase or rate-and-term refinance through select lenders, with the strongest files earning the top of the range. An asset-depletion alternative runs to about 80% LTV on a primary residence. Every figure here varies by lender and program — guidelines, property type, leverage, and credit profile all apply.

On an owner-occupied cash-out, whether a primary residence or second home, the ceiling is up to 80% LTV with a fixed expense ratio, or 75% with an accountant-prepared ratio, depending on loan size and credit. An investment-property cash-out tops out around 75% LTV. Investment purchase leverage on bank-statement documentation varies by lender, so treat any number as something to confirm file by file. Loan sizes generally run from $125,000 to $3,500,000, with reserves commonly around 6 months of the housing payment.

Occupancy also decides the disclosure regime. An owner-occupied file is a consumer mortgage, so TRID applies. A bank-statement loan on a non-owner-occupied rental, including a short-term rental, is business-purpose and TRID-exempt. Consumer mortgage licensing for this lane covers 16 states.

When a DSCR Loan Beats Both Windows

Bank statement loans qualify the borrower. A DSCR loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines. If your investment property’s rent comfortably covers its monthly obligation, the personal income math, and the 12-versus-24 debate, may not matter at all. Some programs also accept coverage below 1.00 through select lenders, though leverage and terms adjust.

Bank statements make more sense when your own income has to carry the file, such as an owner-occupied purchase or a property that does not cover its own payment. The complete DSCR loans guide explains how the two lanes divide.

Investors adding several financed properties feel this most. Each added mortgage lands in your personal debt-to-income ratio on a bank statement file, while a DSCR file leans on the property itself.

The Verdict

Pick 12 months if your income is rising, stable, or your latest year is your best. Pick 24 months if deposits are seasonal or lumpy, or if an earlier peak outweighs a softer recent stretch. If neither window gives a clean number, the file may belong in a different lane entirely.

Don’t choose by instinct. Run both averages, clean the deposits first, and see which window an available program will take. Tax treatment can depend on how the funds are used and how the property is held; investors should keep clear records and speak with a qualified tax professional before relying on any deduction.

If you are self-employed and want to see how the numbers work, Lendmire can help you compare bank statement loan options based on your deposits, the property, credit profile, leverage, and your goals.

About Lendmire

As a DSCR and non-QM mortgage broker, Lendmire — NMLS# 2371349 — connects investors with wholesale lending channels across 41 markets, including Washington, D.C. The property’s rental income, not the borrower’s tax returns, is central to lender review, which works for self-employed operators and portfolios beyond four financed properties. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.

References

1. CFPB Regulation Z, 12 CFR 1026.43

2. eCFR, 12 CFR 1026.43