Affordability assessment

An affordability assessment is the test a lender applies to determine whether an applicant can meet the proposed repayments out of income remaining after living costs and existing debt obligations, without hardship and without needing to borrow again. It answers a narrower question than creditworthiness: not whether the borrower is likely to repay, but whether they are financially able to.

The distinction matters because a borrower can have an excellent repayment record and still be unable to afford a new loan. Willingness and capacity are separate variables, and affordability measures only the second.

Affordability vs. creditworthiness vs. eligibility

• Eligibility — Question answered: Does the applicant meet the basic criteria to apply? | Primary evidence: Age, residency, minimum income, employment status.
• Affordability — Question answered: Can the applicant service the repayments from available income? | Primary evidence: Income records, expenses, existing obligations.
• Creditworthiness — Question answered: Is the applicant likely to repay, given their history and character? | Primary evidence: Credit bureau data, repayment track record, references.

An application can pass eligibility and creditworthiness and still fail affordability. Lending in that situation is the pattern that produces distressed borrowers with clean prior records — and in a growing number of jurisdictions, it is the pattern that attracts regulatory sanction.

The core calculation

Every affordability method reduces to the same arithmetic, whatever the local terminology:

1. Establish gross income — salary, business net income, rental income, remittances, pension, verified secondary income.
2. Deduct statutory and mandatory items — income tax, social security and pension contributions, health insurance levies, union dues, court-ordered garnishments.
3. Deduct necessary living expenses — housing, utilities, food, transport, school fees, medical costs, dependants' support.
4. Deduct existing debt service — every current loan instalment, credit card minimum, overdraft servicing cost, hire purchase payment, and informal borrowing where it can be established.
5. Arrive at disposable income — what remains and is genuinely available for a new obligation.
6. Apply a buffer — a margin retained against income variability and unexpected costs, rather than lending against the last unit of surplus.
7. Compare against the proposed instalment — the loan is affordable only if the instalment fits inside the buffered surplus.

Two methodologies

Ratio-based (income multiple) approach. The proposed instalment, or total debt service, is capped at a fixed percentage of income. It is fast, easy to automate, and easy to explain to applicants and regulators. Its weakness is that a fixed percentage means very different things at different income levels: thirty percent of a high income leaves a substantial cushion, while thirty percent of a subsistence income may leave nothing to live on.

Residual income (surplus) approach. Actual living costs are deducted and the assessment is made on what is left in absolute terms, against a minimum acceptable surplus. This is more accurate, particularly at lower income levels, but requires reliable expense data and a defensible view of what minimum living costs actually are.

Most lenders use both: a ratio as a fast screen, and a residual income calculation as the binding test. Regulators in several markets have moved toward requiring the residual income method specifically, precisely because ratio caps understate hardship at the bottom of the income distribution.

Key affordability ratios

• Debt-to-income (DTI) — Total monthly debt obligations divided by gross monthly income.
• Debt service-to-income (DSTI) — Total debt repayments divided by net income. Usually the more meaningful of the two, since gross income is never available to spend.
• Instalment-to-income ratio — The single proposed repayment as a share of income, used where full obligation data is unavailable.
• Residual income — The absolute currency amount remaining after all deductions, tested against a minimum threshold rather than a percentage.
• Debt service coverage ratio (DSCR) — For business borrowers, net operating income divided by total debt service. A DSCR of 1.0 means income exactly covers repayments with no margin, which is not a passing result.
• Expense-to-income ratio — Declared living costs as a share of income, used as a plausibility check. An applicant declaring living costs of five percent of income is either misreporting or supported by someone whose support has not been documented.

Evidence and verification

An affordability assessment built on unverified applicant statements is a formality, not a control. Common evidence sources:

• Bank statements — typically three to six months, analysed for income regularity, existing debit orders, overdraft dependence, and returned payments.
• Payslips and employer confirmation — for salaried applicants, with attention to how much of the pay is variable.
• Credit bureau reports — to capture obligations the applicant did not disclose.
• Mobile money transaction history — increasingly the richest income record available for informally employed borrowers.
• Business records — sales books, stock counts, supplier invoices, till records, and a physical business visit.
• Utility and rent receipts — to corroborate declared housing costs.
• Declared expense form — the applicant's own statement, benchmarked against statistical living cost data rather than accepted at face value.

Undisclosed borrowing is the largest single source of error. Applicants under-report obligations both deliberately and, in the case of informal or family borrowing, because they do not think of it as debt.

Assessing irregular and informal income

Standard affordability arithmetic assumes a stable monthly income. Most borrowers in emerging markets do not have one. Microfinance institutions (MFIs) and small business lenders adapt in several ways:

• Averaging across a full cycle. For seasonal income (such as farming, school-term trade, or festival-driven retail), the assessment period must cover a complete cycle, not just the three strongest months.
• Matching the repayment schedule to the income pattern. A borrower with harvest-linked income can afford a substantial annual repayment and no monthly one. Forcing a monthly instalment onto lumpy income manufactures arrears that better structuring would avoid.
• Discounting volatile income. Applying a haircut to variable earnings (such as commissions, piece work, or trading margins) before treating them as available.
• Assessing the household, not the individual. Where income and expenses are pooled across an extended household, an individual-level assessment misstates both sides: additional earners raise capacity, while additional dependants lower it.
• Counting remittances carefully. Remittance income is real but discretionary at the sender's end, and is usually discounted rather than counted in full.
• Recognising business-household blending. In micro-enterprises, business and household finances are one pot. Assessing business cash flow without deducting household consumption overstates capacity substantially.

Stress testing and buffers

A responsible assessment does not test only today's numbers. Standard stresses:

• Interest rate rise — for variable rate lending, testing the instalment at a materially higher rate than the one offered.
• Income shock — testing at reduced income, particularly where earnings are variable or the employer is a single concentrated source.
• Cost inflation — testing against higher food, fuel, transport and school fee costs.
• Balloon and step-up repayments — testing the largest instalment in the schedule, not the first or the average.
• Foreseeable change — a known upcoming event such as retirement, contract expiry or a new dependant.

The buffer retained after all this is not waste. It is the difference between a portfolio that absorbs a bad season and one that does not.

Regulatory context

Affordability assessment has moved from good practice to legal obligation across many markets. Common statutory features:

• A duty to assess affordability before extending consumer credit, with the burden of proof on the lender.
• Prescribed minimum evidence, often including verified income and a documented expense assessment.
• A requirement to retain the assessment file for a defined period.
• Consequences for failure that can include unenforceability of the credit agreement, refunds of interest and charges, fines, and licence conditions.

Some jurisdictions treat lending without a proper assessment as reckless lending, a defined offence rather than a matter of commercial judgement — South Africa's National Credit Act is the most developed African example, and consumer credit regimes in the United Kingdom and the European Union impose comparable creditworthiness assessment duties. Others regulate the outcome instead, through caps on total debt service ratios or on the total cost of credit.

The practical point for lenders operating across borders is that the assessment must satisfy the strictest applicable regime, and must be documented well enough to be reconstructed years later by someone who was not present.

Common failures

• Gross income used instead of net. Inflates apparent capacity by whatever the tax and statutory deduction burden is.
• Living expenses taken from the applicant's declaration alone. Applicants under-declare when they want the loan.
• Existing obligations captured only from the bureau. Informal and family borrowing is invisible there.
• The strongest three months used for seasonal income. Produces an affordability figure the borrower can meet for one quarter a year.
• No buffer. Lending to the exact surplus leaves zero tolerance for a single unexpected cost.
• Assessment done once and never revisited. Top-ups and refinancing granted against the original assessment, though obligations have changed.
• Ratio caps applied uniformly across income bands. Systematically over-lends to low-income applicants.
• Assessment treated as documentation rather than decision. The file is complete, the numbers fail, and the loan is approved anyway.

That last item is the one to watch. Where override rates on affordability failures rise, arrears follow with a predictable lag.