I am on a KITAP (Spouse sponsored) But i haven't made any nuptial agreement yet. Can I still buy a land in my Indonesian wife's name?
No (assuming 'Hak Milik" land) . You must have a wealth separation agreement first in order to buy in your Indonesian wife's name , as just now anything bought would be jointly owned and by Law foreigners cannot own any percentage of 'Hak Milik' land (except if inherited) .
Note: I will become an Indonesian citizen next year. In this case, is it okay if my wife buys the land first (now), and then, when I become an Indonesian citizen, we'll both have the land?
a) To buy now with wealth separation agreement , it will be 100% owned by your Indonesian wife .
b) After you become Indonesian :
1. without wealth separation , each will own 50% .
2. with wealth separation you can own 100% (if you buy in your name only) .
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If for some reason you must buy now but don't want it to be owned 100% by your wife , I guess (not sure about) you can make a legal document stating you lend the money to your wife , so later when you become Indonesian you can buy the land from her in exchange of her debt (but you two will have to pay land transaction's tax around 3 times more - first time as the buyer , second time as buyer & seller) .
Probably the IA's idea of gift is not relevant as according to
https://www.hukumonline.com/klinik/...am-transaksi-jual-beli-tanah-lt4c68025b4b085/, the cost for the land transfer are income tax + BPHTB (Land and Building Acquisition Fee - which is related to transfer of rights due to sale and purchase; exchange; grant; testamentary grant; inheritance,..) + notary's fee . Gift could get income tax exemption only if she gives the property to her relatives in first degree (parent, brother, sister, or child) .
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Omnibus Law (UU no.11 Year 2020) , Article 111 (revision of Income Tax Law) - free translation
Article 4
(2) The following income is subjected to final income tax:
d.
income from property transfer transactions of land and/or buildings, construction service businesses, real estate businesses, and land and/or building rentals; and
(3) The following are
exempt from income tax :
a.2.
gifted property received by blood relatives in a direct line of one degree, religious bodies, educational bodies, social bodies including foundations, cooperatives, or individuals who run micro and small businesses, the provisions of which are regulated by or based on the Regulation of the Minister of Finance, as long as there is no relationship with business, work, ownership or control between the parties concerned;