No need to fill any form
When you purchase a property in Chile the IRS ask you to justify where you obtained the money. Not taxes involved in the purchase but you have to explain how you obtained the money, I just find and interesting document in the IRS website
http://www.sii.cl applied to aliens:
RENTA – ACTUAL LEY SOBRE IMPUESTO A LA – ART. 3°, ART. 10°, ART. 20°, N° 3, ART. 42°, N° 2, ART. 70° – CÓDIGO DE PROCEDIMIENTO CIVIL, ART. 345° – CIRCULAR N° 8, DE 2000. (ORD. N° 689, DE 16.03.2005)
How to justify incomes earned abroad to pay expenses or investmentes in Chile
Individuals who had no domicily nor residency in Chile during -at least- 3 consecutive years, and not earned incomes from national origin, and who declares that his expenses or investment has been paid with foreighn incomes, not taxed in Chile, they may acreditate the origin with any legal proof. However in case they present public documents originated out of Chile, it will be not necesary to legalize them as art 345 of Codigo Civil requires. Those incomes are not taxable in Chile if the aplicant had not domicily nor residency in Chile, are not subjet to income tax in Chile, however their profits in Chile will be taxable
-Certificates and documents , such as work contracts and salary receipts from foreigner employers, change receipts from casas de cambio or banks, passport and certificado de extranjeria are fit to prove the origin of funds, The tax service cannot reject a priori the admisibility of those documents.
Note that they use the term "domicily or residence", this mean that if you have domicily in Chile (even not residence) after the 3 years holliday you are subject to income tax. Bottom line, you have to worry only after the 3 years holiday, if you care not to make investments such as properties, cars or depositos a plazo, you may live forever as "no income" person