CardUp rental transaction without tenancy agreement

Trying to make a rental transaction on CardUp with my credit card to seek points- I don't have a formal tenancy agreement since it's my girlfriends own house, so the bank account that I'm transferring to is the house owner. Will house ownership documents & matching bank account statements ,along with proof of residency at the same location at my end work for documentation proof?

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We both live in the same location and I help her with the mortgate therefore no formal tenancy agreement, but have documents to prove that I just moved in (was renting previously)

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Alternatively should I just share a mock tenancy agreement or is that not ethical/legal?

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Has anybody had any experience with CardUp rental transactions before?