Mortgage preapproval vs prequalification
By David Chen · Published October 11, 2026
The two words get used interchangeably in conversation and they are not the same document. Prequalification is an estimate built from numbers you supply; preapproval is a decision built from numbers the lender has checked. Both are usually expressed through the same debt-to-income ratios, so the method is not what differs. What differs is the single input those ratios divide: income.
That sounds like a small distinction until you follow it through the arithmetic. A lending decision is roughly income divided by a payment coefficient, and anything that shrinks the numerator gets multiplied on the way out. On the example below, a $19,800 reduction in recognised income removes $60,361 from the price you can finance — three times the income itself.
Two definitions of the same payslip
Suppose you earn $132,000 a year, and 30% of that arrives as bonus or commission rather than salary. Stating your income as $132,000 is accurate. Whether a lender will use all of it is a separate question, because variable pay has to be evidenced over time, and the portion that is accepted is often discounted.
| Income | Stated | How it is treated | Recognised |
|---|---|---|---|
| Base salary | $92,400 | Counted in full | $92,400 |
| Bonus and commission | $39,600 | Half counted | $19,800 |
| Total used for DTI | $132,000 | — | $112,200 |
A worked example: $132,000 stated, of which 30% is variable pay counted at half. How much of a variable component is recognised is set by the lender and the income type, not by a general rule — the discount is an input here, not a finding.
The gap is $19,800 a year, or 15.00% of the stated figure. Nothing about your finances has changed; the difference is entirely in which of two equally defensible definitions of income is being used.
What that gap does to the price you can shop for
Now put both incomes through the same ratios, with the same debts, the same down payment and the same rate. Everything except the income is held constant, so every dollar of difference in the outcome is the income definition:
| Basis | Income used | Maximum price | Maximum loan | Housing budget |
|---|---|---|---|---|
| Prequalification letter | $132,000 | $435,620 | $375,620 | $3,080.00 |
| Underwritten preapproval | $112,200 | $375,259 | $315,259 | $2,618.00 |
| Difference | $19,800 | $60,361 | $60,361 | $462.00 |
$60,000 down, 6.50% over 30 years, $650 of other monthly debt, property tax at 1.10% a year, insurance at $1,800 a year, mortgage insurance at 0.50% a year. Front-end ratio 28%, back-end 43%. Produced by our calculator and independently recomputed.
Both rows in that table are the same person on the same day. The difference between them is not a change in circumstances — it is the difference between shopping with a letter produced from stated income and shopping with one produced from verified income. If you make an offer on the strength of the first row and the second row turns out to be the binding one, the shortfall arrives at the worst possible moment.
The second gap: the rate is not locked yet
Even a properly underwritten preapproval has a shelf life, because it is calculated at a rate you have not locked. Hold the income at the verified figure and move only the rate:
| Rate | Maximum price | Maximum loan | Housing budget | Against 6.00% |
|---|---|---|---|---|
| 6.00% | $389,247 | $329,247 | $2,618.00 | — |
| 6.25% | $382,141 | $322,141 | $2,618.00 | −$7,106 |
| 6.50% | $375,259 | $315,259 | $2,618.00 | −$13,988 |
| 6.75% | $368,595 | $308,595 | $2,618.00 | −$20,652 |
| 7.00% | $362,140 | $302,140 | $2,618.00 | −$27,107 |
Verified income of $112,200 held constant; only the rate changes. The housing budget is identical in every row because it is set by the front-end ratio against income, not by the rate. Produced by our calculator and independently recomputed.
Three-quarters of a point removes $20,652 from the price you can finance; a full point removes $27,107. And notice the column that does not move: the housing budget is $2,618.00 in every row. That is the whole mechanism in one table. A lender does not decide what you can pay and then find a house — it caps what you may pay as a share of income, and the rate decides how much loan fits underneath that cap.
What this arithmetic leaves out, on purpose
- The lender’s ceiling is not your budget. Both rows above are the maximum a ratio permits, not the maximum you should spend. A ratio ceiling leaves nothing for the months when the roof, the car and the boiler all fail together, and it says nothing about what you actually want to spend on housing.
- How much variable pay gets recognised. The half used here is an example, not a rule. It varies by lender and by income type, and it is normally documented somewhere in the loan file — worth asking about explicitly rather than inferring from the letter.
- Everything else in the file. Assets, credit history, employment history and the property itself all feed the eventual decision. The ratios modelled here are the part that has a computable relationship with the price, which is why they are the part on this page.
- Programme-specific rules. Loan limits, insurance requirements and allowable ratios differ between conventional and government-backed programmes, and between lenders within a programme. See FHA versus conventional for how the structure changes on the same rate.
How to use this
- Ask which income figure was used. That single question explains most of the distance between a prequalification estimate and an underwritten decision. If any part of your pay is variable, ask how much of it was counted.
- Work out your own ceiling with the affordability calculator and keep the result for use as a budget rather than a target. Then read how much house you can afford for why the approved figure and the sensible figure are rarely the same.
- Understand the ratio you are being measured against with the debt-to-income guide, including which debts count, because paying down a small instalment debt can move the ceiling more than saving the same money.
- Lock when you are ready to commit, not before. The rate table above is the cost of leaving it open; a lock has its own cost. The trade is between a known ceiling and a fee, and it is worth making deliberately.
One more check worth running before you offer: the appraisal, not the price, is what the loan is eventually measured against. What if the appraisal comes in low prices the gap between the two, because that gap arrives in cash and it is not in any preapproval letter.
The short version
Prequalification and preapproval run the same ratios on different definitions of income. On a $132,000 income with 30% variable pay, being credited with 50% of the variable portion takes the recognised figure to $112,200, which takes the maximum price from $435,620 to $375,259 — a difference of $60,361, or three times the income in dispute. A further 0.75 points on the rate removes $20,652 more, while the monthly housing budget stays fixed at $2,618.00 throughout. The letter is a range; the ratio is the constraint; and the rate decides how much house fits inside it.
Frequently asked questions
What is the difference between prequalification and preapproval?
Prequalification is an estimate produced from figures you supply; preapproval is a decision produced from figures the lender has verified. Both are usually expressed through the same debt-to-income rules, so the difference is not the method — it is what counts as income. Bonus, commission and overtime are frequently counted at a discount, and any discount is applied before the ratios are calculated, which means it propagates straight through to the maximum loan. On the example here, $19,800 of income that is not recognised costs $60,361 of buying power.
Does a preapproval guarantee the loan?
No. A preapproval is an assessment of your finances at a point in time, conditional on the property appraising, on your circumstances not changing, and on the terms in the eventual commitment letter. Its value is that it converts an estimate into a documented borrowing ceiling, which is what sellers are reading when they compare offers. It is not a commitment to lend on any particular property.
Why does the monthly payment stay the same when rates rise?
Because the constraint is the ratio, not the payment. Lenders cap housing costs as a share of monthly income, so the budget for housing is fixed by your income before any rate is considered. A higher rate does not raise the budget — it reduces the loan that fits inside it, and therefore the price you can offer. On this example the housing budget is $2,618.00 a month at every rate from 6.00% to 7.00%, while the price it supports falls from $389,247 to $362,140.
How much does a rate change cost between prequalification and closing?
On this example, a move from 6.00% to 6.75% removes $20,652 from the price you can finance at the same monthly budget, and a full point to 7.00% removes $27,107. Rate movements of that size over a two-month shopping period are ordinary rather than unusual, which is why the gap between what a letter says and what a rate lock fixes is worth understanding before you make an offer.
What should I do with a prequalification letter?
Treat it as a shopping range rather than a budget, and ask which income figures were used to produce it. If any part of your pay is variable, ask how much of it was counted, because that single input explains most of the difference between the two numbers on this page. Then work out your own ceiling from your own budget rather than adopting the lender's, because the lender's ceiling is limited by a ratio rather than by what you want to spend.
Related guides
- How much house can I afford? — Why the price a lender approves is not the price you should pay, how the debt-to-income rules work, and what the monthly figure has to cover beyond principal and interest.
- Debt-to-income ratio — How front-end and back-end ratios are built, what counts towards them, where the commonly quoted ceilings come from, and what each ceiling buys in house price.
- What if the appraisal comes in low? — A $405,000 appraisal on a $420,000 contract leaves a $13,500 cash gap — and the gap is LTV × the shortfall, so a smaller down payment means a bigger bill. All three ways out, priced.
- How to compare loan offers — Why the headline rate is not the comparison, the three numbers that are, and how to work out whether discount points are worth paying.
Run your own numbers in the loan calculator.
Calculators for this topic
- Home affordability calculator — Works the mortgage question backwards: start from your income, debts and down payment, and find the price you can actually carry rather than the price a lender will approve.
- Mortgage calculator — Monthly payment with property tax, home insurance, HOA and PMI folded in — the number that actually leaves your account, not just principal and interest.
- Amortization schedule — The full month-by-month and year-by-year breakdown of a fixed-rate loan, and how much interest an extra payment removes from the end of it.
This guide is educational and is not financial advice. Figures were produced by our calculator and independently recomputed before publication; your lender's own documents govern your loan. Spot an error? Tell us — see also our disclaimer.