A Bonus and a Salary Payment Are the Exact Same Rupiah. You Don't Treat Them the Same Way
5 min read
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5 min read
Your salary lands on the 25th. You pay rent, food and the usual bills. You count every rupiah.
Then a Rp10 juta bonus lands. Within a week, it is a new phone, a trip, or a nice dinner for ten. You would never have spent Rp10 juta of your salary that way.
But money has no memory. A rupiah from a bonus is the same rupiah as one from your salary. The habit of treating them differently is called mental accounting. This post shows how it works, what the research says, and a simple way to stop it from quietly draining your savings.
Mental accounting is the habit of sorting money into separate "pots" in your head. The pots are not based on what the money can do. They are based on where it came from or what it is for.
Common pots: "salary", "bonus", "THR", "tax refund", "gift", "side income". Each pot gets its own rules. Salary is for bills. A bonus is for fun.
The idea comes from economist Richard Thaler. In 2017 he won the Nobel Prize in Economic Sciences, partly for this work. The Nobel committee described it as people building separate mental ledgers and looking at the narrow effect of each choice, rather than the effect on their whole finances. (Royal Swedish Academy of Sciences, 2017 press release; read through a search summary, not the full text.)
Your brain likes simple rules. "Bonus is extra" is a simple rule. It is also wrong.
A bonus is not extra. It is income you could have used for a goal, a debt, or an emergency fund. The label "extra" is a story. The story makes spending feel safe.
Here is how the pots can behave. This table is an illustration of the idea, not a result from one study:
| Mental pot | How it feels | What can happen |
|---|---|---|
| Salary | Serious, already planned | Goes to bills and fixed costs |
| Bonus or THR | A reward, "extra" | Spent on wants |
| Tax refund | Found money | Spent fast |
| Gift or inheritance | Special, untouchable or "play" money | Either frozen or spent freely |
None of this is a rule of nature. It is a habit. That is good news, because habits can be changed.
Researchers have tested this in simple ways.
One study looked at an online grocery store. Milkman and Beshears (2009, Journal of Economic Behavior & Organization) compared what customers bought when they used a $10-off coupon and when they did not. When a coupon was used, spending went up by $1.59 on average. The extra spending went to items the customer did not usually buy. Small, unexpected savings seemed to unlock small treats. (Milkman and Beshears, 2009; I read the abstract through a search summary, not the full paper.)
Another line of research looked at how money is described. Nicholas Epley and Ayelet Gneezy (2007) reported that income described as a bonus, a plus on top of the normal situation, was spent more readily than the same income described as a rebate, a return to the normal situation. The amount was identical. Only the label changed. (Abstract seen through a search summary; I did not open the paper.)
Both results point the same way. People do not treat money as one big pile. The label changes the choice.
This is NetWort arithmetic with an assumed return. It is not a forecast.
Say you get a Rp10 juta bonus every year for 10 years. That is Rp100 juta in total.
Path A: bonus pot. You spend it each year. After 10 years, you have the memories and the gadgets. Your investments have not changed.
Path B: same money, no special pot. You put the whole bonus into an investment each year. Assume a 6% return per year, with each bonus invested at the end of the year. The math is:
Future value = Rp10 juta × ((1.06¹⁰ − 1) ÷ 0.06) = Rp10 juta × 13.18 ≈ Rp131,8 juta
You paid in Rp100 juta. The extra Rp31,8 juta is growth. This is how compounding works: your returns start earning returns too.
No. A bonus can buy something you truly value. The problem is not spending. The problem is spending without deciding.
The test is simple. Ask: "If this Rp10 juta came out of my salary, would I still buy it?" If yes, enjoy it. If no, the pot is doing the choosing, not you.
Our posts on lifestyle inflation after a raise and on how to split your THR cover two special cases of the same habit.
Open the NetWort Dashboard and look at your total portfolio value in one number. Then add up what you invested this year. Ask one question: did my bonus or THR show up there, or did it go to a different pot? If it did not show up, you have just found your mental accounting.