Is taking other people's money unjustly haram?

Haram Money & business Quran · 2

Short answer

Yes. Allah says: do not consume one another's wealth unjustly (2:188), and that trade by mutual consent is lawful (4:29).

Evidence

Quran

وَلَا تَأْكُلُوٓا۟ أَمْوَٰلَكُم بَيْنَكُم بِٱلْبَٰطِلِ وَتُدْلُوا۟ بِهَآ إِلَى ٱلْحُكَّامِ لِتَأْكُلُوا۟ فَرِيقًۭا مِّنْ أَمْوَٰلِ ٱلنَّاسِ بِٱلْإِثْمِ وَأَنتُمْ تَعْلَمُونَ ﴿١٨٨﴾

And eat not up your property among yourselves in vanity, nor seek by it to gain the hearing of the judges that ye may knowingly devour a portion of the property of others wrongfully.

يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَأْكُلُوٓا۟ أَمْوَٰلَكُم بَيْنَكُم بِٱلْبَٰطِلِ إِلَّآ أَن تَكُونَ تِجَٰرَةً عَن تَرَاضٍۢ مِّنكُمْ ۚ وَلَا تَقْتُلُوٓا۟ أَنفُسَكُمْ ۚ إِنَّ ٱللَّهَ كَانَ بِكُمْ رَحِيمًۭا ﴿٢٩﴾

O ye who believe! Squander not your wealth among yourselves in vanity, except it be a trade by mutual consent, and kill not one another. Lo! Allah is ever Merciful unto you.

This is general information, not a fatwa. For your own situation, ask a qualified scholar.