The share purchase agreement, the closing certificate, the post-closing share register or capitalisation table, both companies' constating documents, and evidence of continuing operations at both sites. Together they must show that the Lake Country company owns and controls the US entity now, not that it intends to.
Which document decides the relationship
The decisive item is whatever shows who holds voting control of the US entity on the filing date. For a share purchase that is the register or capitalisation table after closing, supported by the agreement and any shareholder agreement that allocates board seats or vetoes. Hypothetical example: a Lake Country packing company buys 55 percent of a Washington facility but the agreement gives the remaining 45 percent holder a veto over hiring and capital spending; the file must explain why the Canadian company still controls the subsidiary, or the qualifying relationship may be questioned.
Alongside ownership, USCIS looks for proof that both entities are actively doing business: Canadian payroll records, packing contracts and the Lake Country lease on one side, and US payroll, utility bills and customer invoices on the other. A tax number and a bank account alone do not establish an operating business. Assemble the corporate file at closing rather than reconstructing it months later.