Bank Statements visitor visa

[DexterM]

For a visitor visa, does the applicant/visitor need to provide bank statements for the last 3 months or 6 months?

Mother in-law's application for a visitor visa was refused once as bank statements were not sufficiently showing income and outgoings, thus it was concluded that the entire application was not credible.

I understand that the sponsor should provide proof of income for 6 months and that the applicant's documents are more important to evidence ties to her home country. she is visiting for 2 weeks, will return to her family in Iran.

We improved the organisation of her bank statements in last 3 months but found no official guidance saying what period the applicant's bank statements should cover.

If the Home Office only needs 3 months from applicant and maybe 6 months from sponsor, we can apply again.

If they want 6 months from applicant, we better wait as we want to avoid a further refusal.

Thank you for any advice based on experience or with reference to official guidance.