What to Do With Interest You Already Earned: A Purification Guide

Almost everyone who starts screening their portfolio hits the same wall about a week in. You close the interest-bearing savings account, you sell the bond fund, you switch the brokerage sweep. Then you look at the statements and realize there is a number sitting in your account that came from riba, and nobody told you what happens to it now.

That number has a name in fiqh. The process of dealing with it is usually called tathir or takhallus, and figuring out what to do with interest you already earned is a genuinely separate question from whether you should have earned it. The first is about a past transaction you cannot undo. The second is about a future you can control.

The source text says you keep the principal and give back the increase

The core instruction is unusually explicit. Quran 2:278-279 tells believers to abandon what remains of riba, and then adds that if you repent, fa lakum ru'usu amwalikum, you have your principal sums. The verse draws the line exactly where you would want it drawn: your own capital is yours, the increase over it is not. That single clause is the entire architecture of purification. You are not being told to liquidate yourself. You are being told to strip out the growth that came from the prohibited mechanism.

Quran 2:275 sets up the reasoning by contrasting trade with riba, which is why the fiqh treatment turns on whether a return came from real economic risk or from lending money at a guaranteed markup. And the hadith in Sahih Muslim reported from Jabir, where the Prophet cursed the one who consumes riba, the one who pays it, the one who records it and the two witnesses to it, is what pushes scholars to treat even passive receipt as something you have to actively get out of rather than quietly keep.

There is a second text doing important work here. Also in Sahih Muslim, the Prophet said that Allah is tayyib and accepts only what is tayyib. Contemporary scholars lean on that hadith constantly in this discussion, because it explains why purification is not charity in the normal sense. Tainted wealth given away does not become a good deed for the giver. It just stops being in your possession.

What purification actually does, mechanically

The classical rule for wealth acquired unlawfully is that it goes back to the person it was wrongly taken from. If you cannot identify that person, or the wealth came from a system rather than an individual, the wealth is disposed of for the benefit of the Muslims and the poor.

The reason it goes to the poor rather than into a shredder is a specific juristic argument, and it is worth knowing because it explains a lot of the downstream rules. Ibn Taymiyya and after him Ibn al-Qayyim argued that destroying the wealth serves nobody. Waste is itself blameworthy, the original owner cannot be found, and returning it to the bank simply returns it to the entity that generated the prohibition. So the wealth is directed to public benefit, and the person disposing of it is treated as a conduit rather than a donor. A minority of earlier scholars held that such money should be destroyed or abandoned outright, precisely so no one benefits from it, and you will still see that view quoted. The mainstream contemporary position, and the one AAOIFI operates on, follows Ibn Taymiyya.

Once you see purification as removal rather than giving, the practical rules stop feeling arbitrary.

How to calculate the amount

There are three common situations, and they are not calculated the same way.

Bank interest and cash sweep yields

This one is simple arithmetic. Every dollar of interest credited is purifiable, at 100%. Pull the interest line from your year-end statement or your 1099-INT, add up the credits since you last purified, and that is the number. Do not net it against fees, do not net it against inflation, and do not subtract taxes you paid on it. It is gross interest credited.

Dividends from screened stocks

Almost no operating company is perfectly clean. A retailer books interest on its cash balances, an industrial parks treasury in money market instruments, an airline runs a co-branded credit card. That is why every major screening standard allows a tolerance instead of demanding zero.

AAOIFI Shari'ah Standard No. 21 on Financial Papers, which is the reference document most Shariah boards use for equities, caps income from prohibited sources at 5% of total income and requires that the corresponding portion of what you receive be purified. Dow Jones Islamic Market, S&P Shariah, FTSE and MSCI all run a version of the same 5% impermissible-income limit alongside their leverage screens, even though they differ on the debt denominator (Dow Jones and S&P historically use a trailing 24-month average market cap, FTSE and MSCI use total assets).

The calculation is proportional. If a company generated 2.1% of its total income from interest and you received $600 in dividends from it, the purifiable amount is roughly $12.60. Index providers and many fund managers publish a per-share purification figure each year so you can multiply by shares held instead of rebuilding the ratio yourself. Our screening methodology walks through where those income ratios come from and how the thresholds interact.

Capital gains

Here scholars genuinely differ. One camp requires purification of the impermissible fraction embedded in price appreciation as well, on the logic that the share price reflects retained interest income. The other camp, which includes the position Mufti Taqi Usmani has articulated in his writing on Islamic investment funds, holds that the purification obligation attaches to distributed income and that share price movement is a market valuation rather than a receipt of prohibited revenue. If you want to be cautious, purify dividends as an obligation and treat any gains component as a voluntary extra. Do not let the disagreement become a reason to purify nothing.

Where the money can go, and where it cannot

The governing test is whether you retain a benefit. Purified money can go to a food bank, a medical fund, disaster relief, orphan support, debt relief for the insolvent, water and sanitation projects, or general poverty relief. Those are the uses scholars most consistently permit.

The restrictions follow from the same test:

• Not to people you are already obligated to support. Paying your own parents' or minor children's expenses with purification money discharges a debt you owed, which means you benefited.
• Not as zakat. Zakat must be paid from wealth you legitimately own. Purification money was never lawfully yours, so it cannot satisfy an obligation on your own assets. These are two separate payments in the same year.
• Mosque construction and Quran printing are contested. Many scholars discourage it, arguing that houses of worship should be built from tayyib wealth, and steer purification toward welfare and infrastructure instead. Others permit it under general public benefit. If your local scholar has no strong view, welfare spending is the safer default.
• Not with the expectation of reward. Give it away to be rid of it. The intention is discharge, not sadaqa.

Why you should skip the tax deduction

This is reasoned judgment rather than a ruling from a text, but the reasoning is tight and most contemporary Shariah advisors land in the same place. If you donate $1,000 of purification money to a qualified charity in the United States and claim it as a deduction at a 24% marginal rate, you have recovered $240 of tainted money in the form of reduced tax. The whole point of the exercise was that you retain no benefit from it.

Practically, that means either giving to an organization where you simply do not itemize the receipt, or giving to a recipient that is not tax-deductible in the first place, which conveniently includes direct gifts to individuals in need. Keep your own record of the amount and the date so you can track your obligation year to year, and keep it separate from the giving records you do deduct.

One related point: the tax you already paid on interest income does not reduce what you owe. You purify the gross amount, absorb the tax cost yourself, and treat that cost as the price of having been in the position at all.

The strongest counterargument

There is a real minority view, and pretending otherwise is dishonest.

The historically significant one comes from Abu Hanifa and Muhammad al-Shaybani, who held that riba does not operate between a Muslim and a non-Muslim outside the abode of Islam. Some contemporary jurists have extended that reasoning to Muslims living in Western jurisdictions, concluding that bank interest received there is not subject to the same prohibition. Abu Yusuf disagreed within the same school, and the Maliki, Shafi'i and Hanbali schools reject the exception, so it is a genuine minority even in its own home.

The other is more modern. Muhammad Sayyid Tantawi, as Grand Mufti of Egypt and later Shaykh al-Azhar, argued that returns on certain bank deposit instruments function as a share in the bank's investment profits rather than as classical riba al-nasiah. Al-Azhar's Islamic Research Academy revisited and supported that line in 2002, and it remains influential in Egypt.

Against both stands the near-consensus of contemporary institutional fiqh. The OIC International Islamic Fiqh Academy, at its Jeddah session in 1985, treated all forms of conventional bank interest as prohibited riba, and AAOIFI's standards are built on that premise. If you are using AAOIFI-based screening at all, you have already accepted the framework that makes purification necessary. Adopting the permissive view on your savings account while using AAOIFI thresholds on your equities is not a coherent position.

How FaithScreener surfaces the interest before it becomes your problem

Purification is the cleanup step. Screening is the step that keeps the cleanup small.

When you run a ticker, the report separates the three AAOIFI-style tests: the business activity screen, the leverage and interest-bearing debt ratio, and the impermissible-income ratio that drives your purification math. A company can pass on activity and still hand you a purification bill through its treasury income, which is exactly the case people miss when they screen by industry alone. Seeing the income ratio before you buy tells you roughly what your annual purification obligation on that position will look like.

The multi-faith framework comparison is useful here too, because the treatment of interest is one of the sharpest divergences across traditions. Halakhic screening under the Bais HaVaad two-tier approach distinguishes ribbis between Jews from interest with gentiles and permits structured workarounds through a heter iska. Christian BRI and Catholic USCCB screens focus on business conduct categories and generally do not exclude interest income as such. LDS guidance, going back to Dallin Oaks' 1971 warning about speculation, addresses debt and gambling behavior rather than interest receipt. Islamic screening is the one that generates an ongoing arithmetic obligation on income you have already received. You can run a ticker through the screen and see the income breakdown before you commit capital.

The Bottom Line

Interest you already earned is removed, not kept and not destroyed. Quran 2:279 leaves you your principal and nothing above it, the classical rule for unattributable unlawful wealth sends the rest to the poor, and AAOIFI Shari'ah Standard No. 21 gives you the 5% tolerance and the proportional formula for the dividend case. Calculate gross, give without expecting reward, skip the deduction, and keep it entirely separate from your zakat.

The one thing to hold onto: purification is a discharge, not a donation, and every decision you make about the money should follow from that. If claiming a deduction, paying a family obligation or counting it toward zakat would leave you better off than if the interest had never arrived, that use is off the table.

This is educational research rather than a religious ruling or personalized investment advice, so confirm your specific situation with a qualified scholar or advisor.