What to Do With a Windfall When You Have Debt (With Maths)
If you have debt, a windfall usually does the most good in two places: a small safety buffer first, then your most expensive debt. Every euro paid off a high-rate debt stops interest on that euro for the rest of the time you owe it.
What counts as a windfall?
Windfall is money you did not plan for, such as a bonus, a tax refund, a gift or a cash prize.
It arrives once. That makes it different from a pay rise, which comes every month. A one-off sum can still change your debt a lot, if it goes to the right place.
Should you take your time before deciding?
Yes. A few days costs very little. A rushed choice can cost more. Put the money in a separate account so it does not get spent by accident, then decide.
Should you save some first, or pay it all off debt?
If you have no savings at all, keep a small part aside first.
Emergency fund is cash kept aside only for surprise costs, such as a car repair or a lost week of pay.
The US consumer regulator, the CFPB, explains why this matters. Without savings, a surprise cost often ends up on a card or a loan, which is harder to pay off. It also says a tax refund or a cash gift can help you set up an emergency fund quickly.
The UK’s MoneyHelper gives a general rule: deal with expensive debts and build an emergency fund first. It says you will rarely earn more on savings than you pay on borrowing. So once you have a small buffer, the rest usually works harder on your debt.
Which debt should get the windfall?
Usually the one with the highest interest rate. MoneyHelper says to pay the most off the debt with the highest rate first.
The reason is simple. €1,500 on a card at 19.9% stops about €25 of interest a month. The same €1,500 on a loan at 6.5% stops about €8 a month.
One check before you pay a loan off early: MoneyHelper says to see if there is a penalty for doing so. If there is, compare it with the interest you would save. (More in why paying off early almost always wins.)
What does €1,500 do to real debts?
Here are four debts. You pay €660 a month in total: the minimums plus €150 extra. The extra goes to the highest rate first. (This is the avalanche method. See snowball vs avalanche.)
| Debt | Balance | Yearly rate | Minimum |
|---|---|---|---|
| Card | €4,200 | 19.9% | €120 |
| Car loan | €9,800 | 6.5% | €260 |
| Student loan | €3,100 | 3% | €90 |
| Phone plan | €640 | 0% | €40 |
Step 1: without the windfall. All debts are gone in 30 months. Total interest: €1,802.
Step 2: €1,500 on the card, on day one. The card balance drops to €2,700. Your monthly payment stays at €660, so the freed money rolls on to the next debt as each one clears.
Step 3: run the months again. Each month, add each debt’s interest (balance × yearly rate ÷ 12), pay every minimum, then put what is left on the highest-rate debt.
| Where the €1,500 goes | Debt-free in | Total interest | Interest saved |
|---|---|---|---|
| Nowhere (no windfall) | 30 months | €1,802 | – |
| All on the card | 27 months | €1,244 | €558 |
| €1,000 on the card, €500 kept as a buffer | 28 months | €1,409 | €393 |
| Clear the phone (€640), rest on the card | 27 months | €1,347 | €455 |
| All on the car loan | 27 months | €1,556 | €246 |
Three things stand out:
- The rate matters most. The same €1,500 saves more than twice as much on the card as on the car loan.
- A buffer costs little. Keeping €500 aside still saves €393 and two months.
- Clearing a 0% debt feels good, but costs more. It saves €103 less than putting it all on the card, because the phone plan charges no interest.
What about the money you don’t use on debt?
Keep it somewhere separate and boring. The Australian Government’s Moneysmart suggests a separate, high-interest savings account for emergency money. It also says extra money like a tax refund can be used to boost it.
Then protect your plan. Keep paying the same total each month after the windfall. If you lower your payments because the debt is smaller, you lose part of the saving.
(Not sure whether to save or pay off debt with regular money too? See save or pay off debt first.)
Do this today (10 minutes)
- Move the windfall to a separate account so it isn’t spent by accident.
- If you have no savings, set aside a small buffer from it first.
- List your debts by interest rate, and plan to put the rest on the top one. Check for early repayment fees.
Nada does this maths for you. Add your debts and a one-off payment, and see your new debt-free date. Get Nada
FAQ
Should I use all of my windfall to pay off debt? Not always. If you have no savings, keep a small amount aside first. One surprise bill could put you straight back on a card. Then put the rest on your most expensive debt. In the example, keeping €500 aside and paying €1,000 still saves €393 of interest.
Which debt should a windfall go on first? Usually the one with the highest interest rate. Each euro there stops the most interest. In the example, €1,500 on a 19.9% card saves €558. The same €1,500 on a 6.5% car loan saves only €246. Check for early repayment fees before paying a loan off early.
Is it worth clearing a small 0% debt with a windfall? It can feel good, and it frees up a monthly payment. But a 0% debt costs you nothing in interest. In the example, clearing the €640 phone plan first and putting the rest on the card saves €455. Putting it all on the card saves €558.
What if my windfall is small? It still helps. Any amount paid off a debt stops interest on that amount from the next month. Even €100 on a card at 19.9% stops about €20 of interest a year. A small windfall can also be a good way to start an emergency fund, as the CFPB suggests.
Sources
Read in October 2026.
- MoneyHelper: Pay off debt, save or invest first?
- CFPB: An essential guide to building an emergency fund
- Moneysmart (Australian Government): Save for an emergency fund
Written by the Nada team. Reviewed October 2026.
This is general information, not personal advice.