Invest or Pay Off Debt First? Sort Each Balance by Its Rate

A question I heard constantly when I worked in collections, usually from people who had just made a payment arrangement with me: "Should I have been investing instead?" They had a few thousand dollars in a brokerage app, a credit card at 24 percent, and a vague sense that the market would bail them out. Sometimes it did for a year. Then a bad quarter arrived at the same time as a missed payment, and the account landed on my desk.

The reverse mistake is just as common and quieter. People pour every spare dollar into a 3 percent car loan while skipping a retirement match their employer would have handed them for free. Both errors come from treating "debt" and "investing" as two whole categories, when the real decision happens one balance at a time.

The comparison that actually matters

Paying off a debt is an investment with a guaranteed return equal to its interest rate. Kill a card charging 22 percent and you have earned 22 percent on that money, with no market risk, no taxes owed on the gain, and no chance of a down year. Very few things a beginner can buy offer that.

A broad stock index fund, by contrast, has historically returned somewhere around 10 percent a year before inflation over very long stretches in the US, but that average hides years like 2008, when the S&P 500 fell by roughly 37 percent. The return is expected, not promised. So the honest comparison is a sure thing on one side and a likely but bumpy thing on the other.

That means you are never comparing 22 percent against 10 percent on equal terms. You are comparing a certain 22 against an uncertain 10. When the debt rate is high, the decision is easy. When the debt rate sits close to what you might expect from the market, risk tolerance and taxes start to matter, and reasonable people land in different places.

Sorting each balance, in order

Here is the order I walk people through. It is not the only defensible sequence, but I have yet to see someone hurt by following it.

1. Stay current on every minimum payment. A single payment more than 30 days late can stay on your credit report for seven years. Nothing you invest will outrun that damage, which I covered in what happens after a missed card payment.
2. Keep a small cash buffer. Even one month of essentials stops a flat tire from going on a 24 percent card. The full approach to sizing it is in how much should go into your emergency fund first.
3. Take any employer retirement match. A common formula is 50 cents on the dollar up to 6 percent of salary. That is an instant 50 percent return on the matched dollars, which beats even the worst credit card. Skipping it to pay down debt faster is the one place I tell people to invest first.
4. Pay off anything above roughly 8 percent. This covers almost every credit card, most personal loans, payday and buy now pay later balances that have started charging interest, and many private student loans. Treat these as an emergency, using the avalanche or snowball approach described in our guide to both methods.
5. Split the middle zone, roughly 4 to 8 percent. Many car loans and some federal student loans sit here. Splitting extra money between faster payoff and investing is a reasonable choice, and so is picking one based on how much a monthly bill bothers you.
6. Invest rather than prepay debt under about 4 percent. A mortgage locked at 3 percent in 2021 is cheap money. Paying it down early feels good, but the expected return on a diversified fund, and even on some savings accounts in recent years, is higher.

The 4 and 8 percent lines are rules of thumb, not laws. Someone with a pension and a stable government job can reasonably tolerate more market risk than a freelancer whose income dropped by half last spring.

The advice I would push back on

You will often hear "always pay off all debt before investing a single dollar." It sounds disciplined. In my experience it causes two real problems.

The first is the lost match, already covered above. The second is time. Someone who spends six years clearing a low-rate student loan before opening any investment account has given up six years of compounding that cannot be bought back later. A 25-year-old who puts $200 a month into an index fund and a 31-year-old who starts the same habit will end up far apart at 65, even if their contributions after 31 are identical.

The opposite slogan, "debt is fine as long as your investments earn more," is worse for most people I met. It assumes you will actually keep investing through a crash, and that the debt rate stays fixed. Credit card rates are variable. A card at 19 percent last year might be at 23 percent this year without you signing anything new.

The person who called me most upset was never the one with the most debt. It was the one who had sold investments at a loss in a downturn to cover payments on a card they could have cleared a year earlier.

Taxes change the math a little

Some interest is partly offset by tax breaks, which lowers its effective rate. Student loan interest can be deducted up to $2,500 a year if your income falls below the phase-out limits. Mortgage interest only helps if you itemize, and most households now take the standard deduction, so for them a mortgage rate is simply the rate.

On the investing side, the account you use matters. A dollar going into a traditional 401(k) or IRA may cut this year's tax bill, while gains in a regular taxable account can be taxed when you sell. If you are unsure which account type you would be using, read index funds explained for a first-time investor before you choose a fund.

Credit card interest has no tax offset at all, which is one more reason it goes to the top of the list.

Two quick examples

Dana has a $4,000 card balance at 23 percent, a car loan at 6.4 percent, and an employer offering a match on the first 4 percent of pay. She has about $500 a month spare. A sensible plan is to contribute enough to collect the full match, keep the car loan on its normal schedule, and throw everything else at the card until it reaches zero. After that, the money that went to the card can be split between the car loan and an index fund.

Marcus has no card balance, a mortgage at 3.1 percent, and a federal student loan at 4.9 percent. No match at work. He could put his spare money into an IRA and leave both loans on schedule, or split between the IRA and the student loan. Neither choice is wrong. Prepaying the mortgage would be the weakest of the three options on paper.

Neither example uses real client numbers; they are composites of situations I saw again and again.

Do this before next Friday

Open each of your debt accounts and write down three things for every balance: the amount owed, the current interest rate (not the rate you remember from when you opened it), and whether that rate is fixed or variable. Then check your benefits portal for the exact match formula. With that one page of numbers in front of you, the order above will tell you where your next spare dollar goes, and you will have stopped guessing.