How a Lender Sizes Income on a 5/1 ARM Bank Statement Loan

The Quick Read: A lender builds one monthly income figure from 12 months of deposits, removes anything that is not real income, applies an expense factor to business accounts, and averages the result. The 5/1 ARM does not change how deposits are counted. It changes which payment that income has to support, and on an owner-occupied file the payment is tested at a higher rate than the introductory one.

• Income comes from deposit averages, not from tax-return net income.
• Transfers, loan proceeds and unexplained deposits come out before anything is averaged.
• Business statements get an expense factor. Personal statements usually count at or near full value once cleaned.
• The ARM sets the payment the income must cover. It never raises the income.
• Occupancy decides the disclosure regime: owner-occupied files are consumer mortgages, non-owner-occupied rentals are business-purpose.

Key Terms Defined

Qualifying income: the single monthly figure a lender credits you with after cleaning and averaging your deposits.

Eligible deposits: deposits the underwriter accepts as earned income, not transfers, refunds or loan proceeds.

Expense factor: the share of business deposits the lender treats as operating costs, so only the remainder counts as income.

Ownership share: the percentage of the business you own, which limits how much of its income you can claim.

Lookback window: the number of consecutive monthly statements reviewed, commonly 12 for the programs Lendmire places files with.

Fully indexed rate: the index plus the margin that applies after the ARM adjusts. It is the rate the ARM will move toward after the fixed period ends.

Debt-to-income (DTI): monthly debts, including the new housing payment, divided by qualifying income.

What Is a 5/1 ARM Bank Statement Loan?

It is a mortgage with an introductory fixed period of five years, then yearly adjustments, qualified on bank deposits instead of traditional personal-income documentation. Two separate questions sit inside it. Income is sized from deposits. The payment that income must support is sized from the ARM structure.

Self-employed borrowers use this route because tax-return income is often far below real cash flow after write-offs. Across the wholesale network, the loan is reviewed on documented income under the applicable program, subject to lender guidelines. Most programs ask for 12 months of business or personal statements. Loan sizes run roughly $125,000 to $3,500,000, and reserves commonly sit around six months of the housing payment.

Lendmire is a broker. It arranges these files through select lenders, and each lender underwrites its own way. Nothing here is a commitment to lend.

How Does the Lender Build the Income Number?

The lender runs the same sequence on nearly every file: pick the statements, clean the deposits, apply the expense factor, apply ownership, then average. One explainer on deposit-based income describes the formula as total eligible deposits, reduced by the expense factor, multiplied by ownership share, divided by the months covered.

1. Choose the window. The underwriter takes consecutive, complete statements. A missing page or a skipped month stalls the file.

2. Pick the account type. Personal, business or commingled. The type decides whether an expense factor applies.

3. Scrub the deposits. Transfers between your own accounts, cash advances, loan proceeds, tax refunds and one-time asset sales come out. Large or unusual deposits stay out unless sourced.

4. Apply the expense factor. Business deposits are discounted by a percentage. The lender sets it, not the borrower. Trade coverage of non-QM lending gives 50% as an example of a standard factor and notes a lower one can be supported by a P&L or a third-party tax professional’s expense statement. Treat 50% as an illustration of the method, not a number any lender is bound to use.

5. Apply ownership. A partial owner gets credit only for their share.

6. Average. The result is one monthly qualifying figure.

7. Size the payment. That figure meets the housing payment and other debts in the DTI calculation.

The formula in one line: eligible deposits × (1 − expense factor) × ownership share ÷ months in the window.

What Gets Scrubbed From Deposits?

Anything that is not earned income comes out, and the cleanup is where most files lose qualifying income. A common error is counting a transfer between your own accounts as income. It counts the same dollars twice.

On personal statements, deposits usually count at or near full value after these removals, because no business expense factor applies. On business statements the expense factor does the discounting. Commingled accounts get the most scrutiny, since the underwriter has to separate personal money from business receipts.

Personal or Business Statements, 12 or 24 Months?

Pick the combination that best reflects real, steady cash flow, then let the lender confirm what its program allows. Many wholesale programs need 12 months. Some offer 24. The window is a choice you can optimize when the program allows one.

A documented low-overhead business can sometimes support a lower expense factor with a CPA or tax preparer letter or a P&L. That letter can move qualifying income a lot. Ask before you assume the default.

Worked Example: Same Deposits, Two Expense Factors

Say a sole-owner consultant has business deposits that average a round number each month after scrubbing. Under a 50% factor, half of those deposits count. Under a 25% factor supported by an accountant’s letter, three quarters count. Same bank, same deposits, 1.5 times the qualifying income.

Now carry it forward. Higher qualifying income lowers DTI against the same housing payment. A borrower who sat above a lender’s DTI limit at the higher factor might fall under it at the lower one. This is why the expense factor is the single input worth documenting before the file goes in. Each lender sets its own DTI cap, so no one number applies across the network.

Where Does the 5/1 ARM Come In?

The ARM matters at payment testing and at the reset, not in the deposit math. A low introductory rate does not stretch your qualifying income. On a consumer-purpose, owner-occupied file the lender tests the payment at the greater of the introductory rate or the fully indexed rate, using monthly, fully amortizing payments. That rule sits in Regulation Z § 1026.43, and the full text is at Cornell’s Legal Information Institute. The regulation also carries separate payment-calculation variants for interest-only and negative-amortization loans.

The practical effect: do not tell yourself the five-year teaser makes a bigger loan possible. The lender prices the DTI off the higher payment.

Agencies treat 5-year ARMs differently. Fannie Mae’s Selling Guide uses its own stress rule for them. That is an agency rule for agency loans, not a template for a bank statement file. How a given non-QM lender stress-tests an ARM follows that lender’s program sheet. Term length follows the same logic: it varies by program, and no one should assume an extended-term structure on an alt-doc ARM.

Where the Rule Breaks: Occupancy and Other Edge Cases

Occupancy decides which regime governs the file. An owner-occupied purchase or refinance, including a second home, is a consumer mortgage, and TRID disclosures apply. A bank statement loan on a non-owner-occupied rental, including a short-term rental, is business-purpose and exempt from TRID. Exempt loans carry no ability-to-repay claim. On those rentals the deposit method is a lender policy choice, not a regulatory requirement. Scope questions belong with compliance counsel.

Other places the general rule bends:

• Uneven or declining deposits. Averaging pulls the figure down. Whether the lender uses a 12-month average, a longer average or a trend test varies by program.
• Commingled accounts and multiple businesses. Documentation expectations rise. Expect extra letters and a clean split of what is business and what is personal.
• Unidentified deposits. Non-QM files must still show a reasonable ability to repay, per Scotsman Guide’s reporting. A pile of unexplained deposits does not do that.
• Cash-out. Leverage drops. On a primary residence the ceiling is up to 80% LTV with a fixed expense ratio, or 75% with an accountant-prepared ratio. A second home tops out at up to 75% LTV. An investment property cash-out tops out around 75% LTV. The up-to-90% figure applies only to a primary-residence purchase or rate-term refinance. Asset depletion, qualifying from liquid assets, can run to about 80% LTV on a primary residence.

All figures are typical ranges from select wholesale lenders, subject to lender guidelines, credit, loan size and property review.

Why Your Number and the Lender’s Number Differ

Borrowers estimate income from gross deposits. Lenders arrive lower, for predictable reasons. They scrub transfers. They apply an expense factor you did not choose. They credit only your ownership share. They average weak months in with strong ones. And each lender has its own overlays, so two lenders can size the same statements differently.

Brokers see many programs side by side, so the pattern is consistent. The same file can clear with one lender and stall with another because of the expense factor alone. Matching the file to the program is most of the job.

Exit Planning on a Five-Year Fixed Period

A 5/1 ARM is a bet that you will refinance, sell or earn into a higher payment before the adjustment. The income sizing at the next refinance will run on fresh statements, not today’s. If your deposits rise, a refinance may qualify on a stronger figure. If they fall, the lender sees that too. Keep the documentation habits that built this file, because you will need them again.

Bank Statement or DSCR for a Rental?

The two loans look at different things. A bank statement loan is reviewed for the borrower on deposits. A DSCR loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines. If the property’s rent supports the payment, DSCR may be simpler, since it does not hinge on your personal deposit history. If your own cash flow is strong but the rent is thin, a bank statement file may fit better. Lendmire’s complete DSCR loans guide covers the rental side. Investment purchase leverage on bank statement documentation varies by lender, and investor-focused leverage guidance belongs to the DSCR programs.

Prep Checklist Before You Apply

• Pull complete statements for the full window, every page.
• Mark and explain transfers between your own accounts.
• Source any large or unusual deposit in writing.
• Separate business and personal activity where you can.
• Ask a CPA whether a letter or P&L can support a lower expense factor.
• Stack your other debts so DTI is clear before the file goes in.

Lendmire’s piece Can Self-Employed Borrowers Get a 5/1 ARM Bank Statement Loan? covers eligibility. Tax treatment varies; consult a qualified professional.

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.

Large documentation gaps cost more qualifying income than any structure choice, so the cleanest statements usually win.

About Lendmire

As a mortgage broker (NMLS# 2371349), Lendmire helps self-employed and high-net-worth borrowers in 16 states qualify on bank statements, a profit-and-loss statement, 1099s or liquid assets instead of tax returns, through wholesale lenders. Lendmire is never the lender; program terms are set by the lender and its guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.

References

1. Docsumo, bank statement income verification

2. Scotsman Guide, non-QM lending

3. CFPB Regulation Z § 1026.43

4. Cornell LII, 12 CFR § 1026.43

5. Fannie Mae Selling Guide B3-6-04

6. Scotsman Guide, non-QM borrowers