Letters, e-mails, pictures together, telephone bills, chats, airplane tickets, visas and stamps (from trips to see each another), etc.
Appendix A
Document Checklist - Immigrant
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9. Proof of Relationship to Sponsor
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If you are being sponsored by your spouse, common-law partner or conjugal partner, you must send evidence of the relationship between you and your sponsor such as wedding photos or proof that you are partners, letters between you and your sponsor, and telephone bills showing contact between you and your sponsor.
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Proof of your sponsor's visits such as airline ticket coupons, boarding passes, copies of pages of your sponsor's passport showing entry/exit stamps.
If you are a common-law partner or conjugal partner, provide evidence that your relationship is genuine and continuing and has existed for at least 12 months prior to your application. Also provide details of the history of your relationship and at least two statutory declarations from individuals with personal knowlegde of your relationship supporting your claim that the relationship is genuine and continuing.