Amprui

Hello, My partner and I both use and share an individual account (under my name) for our shared expenses (mortgage, bills, shopping…etc). That “shared” account offers a linked saving pot, so we have been earning some interest over the last year on the money that wasn’t spent. Recently I learnt about personal savings allowance, and realised I’ve gone over the PSA limit. Therefore, we have both decided to open separate individual CASH ISAS. I understand payments over 3K to a parter are free of tax, as long as they are for shared expenses and origin can be demonstrated, but: can I pay my partner back unlimited amounts of transfers over 3K from that “shared” account free of taxation if we can demonstrate he once transferred it to me? Many thanks