Determining the scope of an individual's total income from capital gains involves considering various factors. However, the key criterion is whether the individual is a resident or non-resident. Let's understand why this criterion is crucial in determining the scope of an individual's total income from capital gains.

Resident vs. Non-resident Status:
1. Resident: An individual is considered a resident if they satisfy the residency criteria specified by the tax laws of their country. Generally, this is determined by the individual's physical presence or the number of days they spend in the country during a tax year.

2. Non-resident: On the other hand, an individual is considered a non-resident if they do not meet the residency criteria. Non-residents may include individuals who reside in another country or spend a significant amount of time outside their home country.

Importance of Resident vs. Non-resident Status:
The resident or non-resident status is crucial in determining the scope of an individual's total income from capital gains due to the following reasons:

1. Taxability: Tax laws vary for residents and non-residents. Generally, residents are subject to tax on their worldwide income, including capital gains arising from any source. Non-residents, on the other hand, may only be subject to tax on capital gains arising from specific sources within the country.

2. Exemptions and Deductions: Residents often have access to various exemptions, deductions, and tax benefits that may reduce their taxable income, including capital gains. Non-residents may have limited or no access to such benefits, which can affect the scope of their total income from capital gains.

3. Tax Rates: The tax rates applicable to residents and non-residents may differ. Residents may be subject to progressive tax rates, where the tax rate increases with the income level. Non-residents, on the other hand, may be subject to flat tax rates or different tax brackets, which can impact the overall tax liability on capital gains.

4. Double Taxation: If a non-resident earns capital gains in a foreign country, they may be subject to taxation in both the foreign country and their home country. However, tax treaties and agreements between countries often provide relief to avoid or reduce double taxation. Determining the resident or non-resident status helps in determining the applicability of such treaties.

In conclusion, the key criterion for determining the scope of an individual's total income from capital gains is whether the individual is a resident or non-resident. This criterion plays a significant role in determining the taxability, exemptions, deductions, tax rates, and potential double taxation applicable to an individual's capital gains.