I think you're asking about a Certificate of Coverage (form CHI/USA 4).
The instructions are in this pdf:
You can try asking online here:
https://www.spensiones.cl/apps/consulta ... nsulta.php
If you were self-employed in Chile, when AFP's weren't required for self-employed people, read pages 68 and 69 in this pdf:
https://www.jct.gov/publications.html?f ... &no_html=1
This is the important part:
Under the Act, wages and self-employment income are exempt
from FICA and SECA to the extent that, under a totalization
agreement with a foreign country, the wages or self-employment income
is subject exclusively to the laws applicable to the Social Security
system of the foreign country. As a result, an individual’s
earnings are exempt from FICA and SECA in cases in which the
earnings are subject to a foreign country’s Social Security system
in accordance with a totalization agreement, but the foreign country’s
law does not require compulsory contributions on those earnings.
The Act establishes that such earnings are exempt from FICA
and SECA regardless of whether the individual elects to make contributions
to the foreign country’s Social Security system.
This is from 2005, so there may be something more recent, but I'm not aware of it. If you read the actual agreement, the language is pretty clear about self-employment. But lots of people still get confused about it. This thread is a good example (and where I found the above JCT info):
https://www.toytowngermany.com/forum/to ... us/?page=5
Also, if Chile won't issue one, the IRS's pub 54 says this:
If the authorities of the foreign country will not issue such a statement, either you or your employer should get a statement from the U.S. Social Security Administration, Office of International Programs, at the website and mailing addresses listed earlier. The statement should indicate that your wages aren’t covered by the U.S. social security system.