You will need to submit more documented evidence of co-habitation than just bank statements.
See the Home Office official guidance below on proving you have been living together in a relationship '
akin to marriage' for 2 years:
"
13. SET5.13 What types of evidence might demonstrate living together and a relationship akin to marriage / civil partnership?
The applicant must provide six pieces of correspondence addressed to him / her and their partner at the same address as evidence that they have been living together during the past 2 years. The items of correspondence should be addressed to them jointly or in both their names. If they do not have enough items in their joint names, they may also provide items addressed to each of other individually if they show the same address for both of them. The documents provided must be originals and should be spread over the whole 2 years; they should also be from at least 3 different sources. Examples of what documentation the applicant could provide are listed below:
Joint commitments, (such as joint bank accounts, investments, rent agreements, mortgage, life insurance policy naming the other partner as beneficiary etc);
Birth certificates or records of any children of the relationship, showing both partners as parents;
Any official correspondence linking both partners to the same address, for example Council Tax, utility bills, Doctors records;
Any other evidence that adequately demonstrates the couple’s long-term commitment to each other.
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https://www.gov.uk/government/publicati ... ners-set05
