Debt-to-Income Ratio | Credit Assessment Guide
Calculate and use debt-to-income ratio for credit assessments in South Africa. DTI, NCA affordability, and consistent bureau-based analysis.
The debt-to-income ratio (DTI) is one of the most widely used metrics in South African credit assessment. For credit professionals—debt counsellors, credit brokers, and credit providers—DTI sits at the centre of affordability analysis, restructuring proposals, and lending decisions. Yet how it is defined, calculated, and applied varies across firms and even across assessors within the same firm. In a regulated environment where Section 81–82 of the National Credit Act (NCA) require proper affordability assessment and prohibit reckless lending, that inconsistency creates compliance risk and undermines the value of the metric. This article explains what DTI means in the South African credit context, how to calculate it correctly, why it matters for NCA compliance, how different roles use it, and why structuring bureau data is essential for consistent DTI calculation at scale. For a broader view of affordability assessment in South Africa, see the affordability assessment guide.
What DTI Means in the South African Credit Context
From a professional perspective, DTI is a measure of the consumer’s debt burden relative to income. It answers the question: what proportion of the consumer’s income is already committed to servicing existing credit? A high DTI suggests limited capacity for new obligations; a lower DTI leaves more room for additional credit or for restructuring existing debt. The metric is not consumer advice—it is a tool for practitioners to compare applicants, assess affordability, and support recommendations.
In South Africa, DTI is used in three main ways. First, as an affordability indicator: does the consumer have capacity for the proposed credit or restructure? Second, as a compliance input: the NCA expects credit providers to assess existing financial means and obligations before extending credit; DTI is a core part of that assessment. Third, as a comparative measure: when assessing many consumers, DTI allows practitioners to rank or segment cases by debt burden and to apply consistent thresholds. The definition of “income” and “debt” therefore matters: the same consumer can produce very different DTI figures—and outcomes—if one firm uses gross income and another net, or if one includes only instalment debt and another all contractual obligations.
How to Calculate DTI
DTI is expressed as a ratio or percentage: total monthly debt obligations divided by monthly income. The formula is straightforward, but the inputs must be defined clearly and applied consistently.
Gross vs net income
Income can be taken as gross (before tax and deductions) or net (after tax and deductions). Net income is generally the better basis for affordability because it reflects what the consumer actually has available to meet obligations. Gross income is easier to verify from payslips and is sometimes used for consistency with bureau or employer data. Whichever definition your firm uses, it must be applied the same way for every assessment. Document whether you use gross or net, and ensure that expense or DTI thresholds are calibrated to that choice. For example, a 40% DTI threshold on net income is stricter than 40% on gross, because net is the smaller figure.
Total debt obligations
Total debt obligations mean all monthly contractual repayments that the consumer is required to make under credit agreements. That includes bond or home loan instalments, vehicle finance, personal loans, credit cards (minimum or contractual payment), store cards, and any other credit facilities that require a recurring payment. One-off or discretionary payments are not included. The figure should reflect current obligations—so if a consumer has fallen behind and the creditor has not yet adjusted the instalment, the contractual instalment (what they are supposed to pay) is typically used, not the reduced amount they are actually paying. This avoids understating the true debt burden. Data for these obligations comes from credit bureau reports—Experian, Datanamix, TransUnion, or others—where account balances, limits, and sometimes instalment amounts are listed. Where the bureau does not provide an instalment, firms often estimate it (e.g. from balance and term) or use a standardised method; that method should be documented and applied consistently.
The formula
DTI = (Total monthly debt obligations ÷ Monthly income) × 100
Result is usually expressed as a percentage. Example: if total monthly debt obligations are R8,000 and monthly net income is R20,000, DTI = (8,000 ÷ 20,000) × 100 = 40%. Thresholds vary by lender and product—often 30–40% of net income for unsecured credit—but the calculation itself should be standardised so that the same inputs always produce the same DTI.
NCA Context: Why DTI Matters for Compliance
Sections 81 and 82 of the National Credit Act are the main drivers for formalising DTI in credit assessment. Section 81 requires credit providers to take reasonable steps to assess the consumer’s existing financial means, prospects, and obligations before entering into a credit agreement. Section 82 prohibits reckless lending—including extending credit when the consumer is already over-indebted or when the credit provider failed to conduct a proper assessment.
DTI is a central part of that assessment. It summarises “existing obligations” relative to “financial means” in a single, comparable number. When DTI is too high, the consumer may be over-indebted; granting further credit without addressing that raises reckless lending risk. The NCR expects credit providers to document how they assessed affordability, what income and obligations they used, and how they reached their decision. Inconsistent or undocumented DTI calculation makes it difficult to show that reasonable steps were taken. For debt counsellors, DTI supports the determination of over-indebtedness and the design of restructuring proposals that bring obligations in line with income. For all parties, a clear, repeatable DTI methodology supports compliance and audit readiness.
How Different Roles Use DTI
DTI is used differently depending on whether you are a debt counsellor, credit broker, or credit provider. The same ratio supports different decisions.
Debt counsellors: restructuring proposals
Debt counsellors use DTI to assess whether a consumer is over-indebted and to build restructuring proposals. They need to see total obligations from bureau data, compare that to verified income, and determine whether current repayments are sustainable. A high DTI supports a finding of over-indebtedness and justifies a proposal to reduce instalments or extend terms. After restructuring, DTI should fall to a level the consumer can sustain. Debt counsellors often work with multiple bureaux and multiple reports over the life of a case; consistent definition of income and obligations, and a consistent formula, ensure that the same consumer is not assessed one way at intake and another way at review.
Credit brokers: pre-qualification
Credit brokers use DTI to pre-qualify applicants before submitting them to lenders. They need to know quickly whether an applicant’s debt burden is within typical lender limits so they can focus pipeline on viable cases. DTI here is a filter: applicants above a threshold may be deprioritised or advised to reduce debt before applying. Brokers may not have the same depth of income verification as the eventual lender, so they often use stated income and bureau-derived obligations. The important point is that the obligation side—the denominator in the ratio—should be calculated the same way for every applicant. When obligation totals are pulled manually from PDF reports, variation between assessors can mean some applicants are misclassified.
Credit providers: lending decisions
Credit providers use DTI as an input to the formal affordability assessment required by Section 81. They typically have verified income and full bureau data. DTI is used alongside other factors—payment history, credit scoring, living expenses—to decide whether to grant credit and on what terms. Internal policy will set DTI limits by product; exceeding the limit may lead to decline or to a different product. For compliance, the credit provider must be able to show how DTI was calculated, what data was used, and how it fed into the decision. Ad hoc or inconsistent calculation weakens that evidence.
Limitations of DTI as a Sole Metric
DTI is useful but not sufficient on its own. It does not capture payment behaviour, credit history, or the timing and structure of obligations.
Payment history indicates whether the consumer has met existing obligations on time. Two consumers with the same DTI may have very different risk profiles if one has a clean payment record and the other has recent arrears or defaults. Credit scores and payment profile strings add that dimension. DTI also says nothing about income stability—whether the income is permanent or temporary, or likely to change. A consumer with a low DTI but unstable income may be riskier than one with a slightly higher DTI and stable employment.
Living expenses are not reflected in DTI; two consumers with the same income and debt can have the same DTI but very different disposable income. Many firms combine DTI with an expense ratio or residual income to get a fuller picture. For a complete assessment, DTI should be used with payment history, scores, and expense context—not as a single gate.
Manual DTI Calculation from PDF Reports: Errors and Inconsistency
In practice, many firms still derive DTI by reading PDF credit reports and typing figures into a spreadsheet or case file. That workflow introduces errors and inconsistency.
PDFs are not structured: balances and instalments sit in tables or narrative text, so the assessor must find each account, decide what counts as a debt obligation, and re-enter the numbers. Misreading a digit, missing an account, or double-counting is easy. Different assessors may include or exclude accounts differently—e.g. a dormant store card or accounts in dispute—so the same report can yield different DTI figures when used by different people or at different times. That variability undermines fairness and makes it hard to defend decisions in an audit. There is also no single source of truth: the DTI may exist only in a note or spreadsheet cell, with no link to which report or accounts were used. Reconstructing it for the NCR or an internal auditor is labour-intensive and often incomplete.
Structured Bureau Data: Automated, Consistent DTI
When bureau data is structured—parsed into consistent fields for accounts, balances, instalments, and income (where available)—DTI can be calculated automatically using the same formula and the same rules for every case. That removes the variability that comes from manual extraction and ad hoc choices.
Structured data means every account is classified consistently: which accounts are included in “total debt obligations,” how instalments are derived when the bureau does not supply them, and how income is combined when multiple sources exist. The formula runs the same way for debt counsellors, brokers, and credit providers, so that the same consumer produces the same DTI regardless of who runs the assessment. Changes over time are traceable: when a new report is pulled, the system can compare DTI to the previous assessment and show whether the consumer’s position has improved or deteriorated. Because the calculation is rule-based and stored with a link to the underlying report, the audit trail is clear: which report, which accounts, which formula, and what result. That supports NCA compliance and defensible decision-making.
Firms that move from PDF-based manual DTI to structured bureau data do not change the meaning of DTI—they fix consistency and auditability. The ratio remains a core input for affordability, over-indebtedness, and lending; it is simply computed the same way across all cases and can be explained and reproduced when required.
Ensure Consistent DTI Calculation Across Your Team
Debt-to-income ratio is essential for affordability assessment, NCA compliance, and fair treatment of consumers. Calculating it consistently requires clear definitions, a standard formula, and bureau data in a form that supports repeatable calculation—not locked in PDFs where manual re-keying and interpretation introduce errors and variation.
Get in touch to see how structured credit data enables consistent DTI calculation across your team and keeps a clear audit trail from bureau report to outcome.