Repayment of Input VAT on unpaid supplier invoices

Hi All, We have some unpaid supplier invoices going back as far as september 2023. They're on the ledger but in dispute as the wholesaler cannot provide proof of delivery. I believe there's a rule whereby she should be crediting out any invoices older than 6 months old that we have not paid, but I cannot find any HMRC guidance on this topic. Would someone be able to shed some light / share the link? Thanks :)

Hi Laura,
Please see the guidance below:
Relief from VAT on bad debts (VAT Notice 700/18)
Thank you.