How to Screen a Stock Like a Scholar: The AAOIFI Rules NZ Investors Rely On

Every halal verdict you get from Zoya or Musaffa, and every holding inside AE Investor, traces back to the same two-part test. Part one asks what the company does. Part two asks how its balance sheet is built, and it turns on three numbers: non-permissible revenue under 5%, interest-bearing debt under 30%, and interest-bearing securities under 30%. Understand those and you understand modern halal equity investing. This guide explains the test the way the tools apply it.

Part one: the business activity screen

The first cut is categorical. A company whose core business is prohibited cannot be owned at any price. The standard exclusion list covers conventional banking, insurance and interest-based lending; gambling; alcohol; pork; tobacco; adult entertainment; weapons; and conventional derivatives trading. A company core to any of these fails immediately, regardless of its financials.

The interesting cases are mixed businesses. A supermarket sells some alcohol; an airline earns some interest on cash; a hotel chain has a bar in every lobby. This is where the 5% tolerance comes in: if non-permissible activity generates less than 5% of total revenue, the majority scholarly position implemented by AAOIFI-based screens allows ownership, on the condition that the impermissible slice of your return is purified, meaning given away to charity. The tolerance exists because a categorical zero would exclude virtually every listed company on earth; the purification duty exists because the tolerance is a concession, not a blessing.

Part two: the financial ratio screen

• Interest-bearing debt must be under 30% of market capitalisation. A company financed heavily by riba is disqualified even if it makes something wholesome, because shareholders are partners in the whole enterprise, including its funding structure.
• Interest-bearing investments and securities must be under 30% of market capitalisation. The mirror rule: a company parking large treasuries in bonds and deposits is earning riba at scale.
• Non-permissible revenue must stay under 5% of total revenue, as above.

Implementations differ at the edges, and honest investors should know it. Musaffa measures the 30% caps against a trailing 36-month average market capitalisation, which smooths out share price spikes. Zoya's Pro tier lets you switch between the AAOIFI default and the S&P, MSCI, Dow Jones and FTSE Russell rulebooks, some of which use 33% thresholds or total assets as the denominator. And Always-Ethical's Strict Ethical Mandate adds a third test of its own: assets making or doing something for the good of humanity must exceed 67% of total assets, with any compliance breach sold the next trading day. Same skeleton, different tightness.

A worked example

Take a fictional listed retailer, KiwiMart, with a market capitalisation of NZD 2 billion. Its annual report shows NZD 900 million of revenue, of which NZD 36 million comes from liquor sales; NZD 500 million of interest-bearing borrowings; and NZD 150 million held in bonds and term deposits. The math: liquor is 4.0% of revenue, under the 5% cap. Debt is 25% of market capitalisation, under 30%. Interest-bearing securities are 7.5%, comfortably under 30%. KiwiMart passes, with a purification duty: 4.0% of any dividend you receive should be given away. If its share price halved while debt stayed flat, debt would jump to 50% of market capitalisation and the stock would fail, which is exactly why compliance alerts matter: verdicts move with markets.

Applying it from New Zealand

Nobody does this from annual reports by hand more than once, which is the educational once. In practice, run every buy through a screener: Zoya for instant free verdicts on US and other covered markets, Musaffa for research depth and the only partial NZX coverage in existence. Our comparison of the two helps you choose, and our broker workflow guide covers the platform side. For NZX shares neither app covers, the manual method above is your only option, and our NZX screening article explains that problem honestly.

The two duties that follow a pass

Questions the screen raises

Why is any tolerance acceptable at all? Because the alternative is exclusion from equity ownership entirely. Modern listed companies operate inside an interest-based financial system: they bank, they hold working capital, they carry some debt. The scholars who developed the ratios in the 1990s judged that minority, non-core impermissible activity does not define a company's essence, provided the investor purifies the tainted fraction and the caps keep the exposure genuinely minor. Serious people disagree with that judgment and avoid equities altogether; the screening consensus is the majority position, not a unanimous one, and knowing that keeps the exercise honest.

Why market capitalisation as the denominator? Convention and practicality: market cap is observable daily, which makes screening continuous rather than annual. Its side effect is the one in our KiwiMart example, where a share price crash can flip a stock non-compliant without the company doing anything. Some standards use total assets as the denominator instead, which moves more slowly, and this single choice explains many of the disagreements between screening apps on marginal stocks.

Does passing the screen make everything about the company halal? No. The screen makes ownership permissible with purification; it does not bless the 4% liquor aisle. The construction is a concession under defined limits, which is why the purification duty is not optional politeness but the price of admission, and why some investors voluntarily hold themselves to tighter thresholds than the standard requires. Tighter is always permissible; looser is where you need a scholar, not an app.

A passing verdict starts obligations rather than ending them. First, purification: the impermissible fraction of your return must be given to charity, and the competing calculation methods are covered in our purification guide. Second, monitoring: a compliant stock can fail next quarter, so alerts or a periodic re-check are part of owning it. Screening is not a certificate you frame. It is a discipline you run for as long as you hold the shares.