As best as -I- can tell, Israel is collecting Palestinian taxes. Here’s another article from a different outlet:
What are the Palestinian funds that Israel collects?
Israel collects Palestinian import tax revenue as agreed to in the 1994 Paris Accords signed by the Palestine Liberation Organisation and Israel. The tax revenue Israel collects is made up of indirect taxes imposed on Palestinian imports. It comes from two primary sources: VAT on goods and import tax on goods brought in from outside Israel.
These are taxes that would normally be collected by a country for transactions within/at their borders, not charity/extra taxes paid for by Israelis. From the Wikipedia article, Israel collects taxes on goods/services that end up in Palestine, and controls/collects tariffs on goods entering Palestine. They tax Palestinian labor both in Israel and in the illegal settlements in OPT. They have also used withholding those taxes as a form of control several times in history and those are listed in the article.
As you note, this situation was only supposed to last 5 years, instead Israel has enforced it for 30 and according to the UN it’s not because Israelis are “giving them free money”. "However, 30 years later, the financial settlement continues to give the Israeli state what the United Nations Conference on Trade and Development (UNCTAD) has called “a disproportionate influence on the collection of Palestinian fiscal revenue, leading to deficiencies in the structure and collection of customs duties resulting from direct and indirect importing into Palestine”.
I am not an expert. I may be wrong. But none of the sources I’m finding frame the issue as Israel withholding charity or bonus payments or anything similar - they all say Israel is holding Palestinian taxes. I only care about proof, so if you can provide it I’ll check it and if it outweighs the evidence I’ve found and linked I’ll change my mind.