The gap between the two numbers
You put your income into a bank's borrowing calculator and it returns a cheerful figure. You apply, and the offer comes back materially lower — sometimes 20% lower, sometimes 40%.
Nothing dishonest has happened. The public calculator and the credit assessment are answering different questions. The public one asks roughly "what could someone on this income afford at today's rate?". The assessment asks "what could this specific person still afford if rates rose sharply, if their spending were at least at a defined minimum, if every credit line they hold were fully drawn, and if their income were treated conservatively?"
Four adjustments do nearly all of the work, and they compound. Knowing them in advance turns a disappointing surprise into something you can plan around — and two of the four are things you can change in a fortnight.
1. The assessment rate
Lenders do not test whether you can afford the loan at the rate you are being offered. They test it at a higher rate, so that a borrower is not immediately in difficulty when rates move. Depending on the jurisdiction and period this is a fixed buffer above the product rate, a regulatory floor, or the higher of the two.
A buffer of around three percentage points has been common. On a 25-year repayment loan the effect is large:
| Rate | Monthly repayment | vs. actual rate |
|---|---|---|
| 5.5% — the rate you would pay | 1,842 | — |
| 8.5% — the rate you are tested at | 2,415 | +31% |
The lender needs your surplus income to cover 2,415, not 1,842. That single adjustment removes roughly a quarter of the borrowing capacity a naive calculation produces, and it is applied before anything else is considered.
2. The living-cost floor
Applications ask what you spend each month. Almost everyone understates it — usually not dishonestly, but because the annual and irregular costs genuinely do not come to mind: insurance renewals, car servicing, dentistry, the boiler, Christmas.
Lenders solved this by refusing to use your figure when it is implausibly low. They apply a benchmark — a statistically derived minimum for a household of your size, in your area, at your income — and assess against the higher of your declared spending and that benchmark.
So declaring 1,400 a month for a couple with two children when the benchmark says 2,600 achieves nothing at all. The assessment uses 2,600. The 1,200 difference is roughly 400,000 of additional repayment capacity over the term that simply is not credited to you.
This has a genuinely useful implication: understating your expenses does not help, and slightly overstating them costs you nothing when you are already above the floor. What does help is reducing the recurring commitments the lender counts separately from the floor — subscriptions, buy-now-pay-later arrangements, personal loans.
3. Credit limits, not credit balances
This is the adjustment that surprises people most, and it is also the easiest to fix.
A credit card with a 15,000 limit and a zero balance is not treated as zero debt. The lender assumes you could draw the full limit tomorrow, and charges a monthly commitment against it — commonly around 3–3.8% of the limit.
At 3.5%, that unused 15,000 limit counts as 525 a month of committed expenditure. Against an assessment repayment of 2,415, that is over a fifth of the entire loan you were applying for, consumed by a card you never use.
Reducing an unused credit limit takes a phone call and clears within days. It costs nothing, it does not require repaying anything, and on a typical application it moves borrowing capacity by tens of thousands. Do it well before you apply, so the reduced limit is showing on your file.
The same logic covers overdraft facilities and any revolving line. Unused capacity is treated as used, because from the lender's point of view it can be.
4. The self-employed penalty
If your income is not a payslip, the assessment gets more conservative in several ways at once.
- Averaging. Two or three years of accounts, averaged — and where income has fallen, many lenders use the lower year rather than the average. A strong recent year does not fully count until it has a peer.
- Net, not gross. Assessment is on profit after expenses, and after tax. The revenue figure that feels like your income is not the figure being used.
- Add-backs are not automatic. Depreciation, one-off costs and director's pension contributions can sometimes be added back to profit, but only if you identify them and the lender accepts them. Nobody does this on your behalf.
- Unpaid tax counts. If you owe tax you have not yet paid, a careful assessment treats it as a liability, because it is one. This is where reserving as you go pays a second dividend: a reserved liability is visibly provisioned rather than an unexplained future claim on your income.
None of this is a judgement about self-employed people. It reflects that variable income is genuinely harder to underwrite, and that the lender is pricing that uncertainty.
Worked example: the same person, two answers
A couple, one salaried, one self-employed
Combined declared income 128,000. Declared living costs 2,100 a month. One credit card, 18,000 limit, balance zero. A car loan at 480 a month with 3 years to run. Product rate 5.5%, assessed at 8.5%, over 25 years.
The website's answer. Roughly 4.5× income, lightly adjusted for the car loan — about 545,000.
The assessment's answer.
| Step | Monthly |
|---|---|
| Net income after tax (self-employed half assessed on averaged profit) | 7,150 |
| Living costs — benchmark floor applied, not the 2,100 declared | −2,850 |
| Car loan | −480 |
| Credit card: 3.5% of the 18,000 limit | −630 |
| Unpaid tax provision on the self-employed income | −390 |
| Surplus available for the loan | 2,800 |
2,800 a month, at the 8.5% assessment rate over 25 years, supports about 348,000 — not the 545,000 the website suggested. A gap of nearly 200,000, with no adverse credit history and nothing unusual in the file.
Now the fixable part. Reduce the card limit from 18,000 to 3,000: the commitment falls from 630 to 105, adding 525 to monthly surplus. Clear the car loan if the savings exist: another 480. Surplus becomes 3,805, which supports roughly 473,000.
Two actions, neither requiring a higher income, worth about 125,000 of borrowing capacity. The card limit alone — one phone call — is worth about 65,000.
What actually moves the number
In rough order of impact per unit of effort:
- Reduce unused credit limits. Free, fast, and usually the largest single gain. Do it months ahead so it is settled on your file.
- Clear small recurring commitments. A loan with 18 months left is counted at its full monthly cost; clearing it converts that whole payment into borrowing capacity, at roughly 120× the monthly figure.
- Close unused accounts and facilities. Same logic as limits, including overdrafts and store cards you have forgotten about.
- Show clean, consistent statements. Lenders read three to six months of transactions. Gambling, frequent buy-now-pay-later, and returned direct debits all cause real problems, and the window is short enough to be worth waiting out.
- If self-employed, get the accounts right and identify add-backs. A broker who knows which lenders accept which add-backs is worth more here than anything you can do alone.
- Extend the term. Increases capacity mechanically and increases total interest substantially. It is a real lever and it has a real price.
What this cannot tell you
- Every lender is different. Assessment rates, benchmark cost figures, card-limit percentages and income treatment vary between lenders and between products at the same lender. Two applications on the same day can differ by six figures.
- The rules change. Assessment buffers and affordability rules are set by regulators and lender policy, and both are revised regularly. Any figure here is illustrative of the mechanism, not current policy.
- Capacity is not approval. Affordability is one test. Credit history, deposit size, the property itself, and the loan-to-value band all sit alongside it, and any of them can decline an application that passes affordability comfortably.
- Borrowing the maximum is rarely the goal. The assessment tests whether you could survive a rate rise. It does not ask whether you would enjoy it, or what happens to the self-employed half of the income in a bad year.