Foreign asset reporting is the compliance area that catches expats most often, because it feels invisible until it very much is not. Two directions matter. Your host country, once you are its tax resident, typically requires declaring worldwide income, foreign bank accounts, investments and sometimes property, often on dedicated forms separate from the main return. And your home country may keep its own claims: the United States taxes citizens globally and requires foreign account reports, India requires resident taxpayers to disclose foreign assets, and many countries have equivalents. The days of quiet offshore accounts are over, since more than a hundred countries automatically exchange bank account information under common reporting standards, meaning your host and home tax authorities increasingly see each other's data.
Penalties for non-compliance are genuinely severe in many jurisdictions, frequently calculated per account per year and sometimes carrying criminal exposure for willful concealment, wildly out of proportion to the tax actually owed on a modest account. The good news: most countries offer voluntary disclosure programs with reduced penalties for people who correct past omissions before being caught.
The practical line: inventory every foreign account, investment, pension and property when you become tax resident anywhere, ask a cross-border tax professional which forms apply in both countries, and file even when no tax is due, since most reporting obligations exist independently of owing anything.