Immigration to the United States is numerically limited. This is controlled by an annual allocation of visa numbers. Each family-based or employment-based immigrant category has its own limit. Additionally, there is a per-country limit of seven percent of the total numbers. The basic rule of chargeability is that one is charged against the quota for the country of his or her birth. This determination is not tied to citizenship or nationality. A person born in a particular country is subject to that country's quota. For example, a potential immigrant is born in India. He subsequently becomes a Canadian citizen. Unless this individual fits within one of the exceptions discussed below, he will still be subject to the backlogged quota for India, even as a Canadian citizen. 

In some circumstances, an immigrant can cross-charge to the country available to his or her spouse (provided that the spouse is immigrating also). For example, cross chargeability would usually be available if a person born in India were to marry a person born in Canada. If a U.S. employer filed an employment-based, second-preference (EB2) petition on behalf of the individual born in India, she or he would be able to use the Canadian chargeability, if immigrating with the spouse. Historically, this would mean immediate eligibility for immigration benefits under the Canadian quota, rather than many years of waiting under the heavily-backlogged Indian quota