Recently we needed some building work done at home by a local, reliable tradesmen, I wasn't at home at the time but gave dp the exact amount of the price of the works in cash plus a tip in a sealed envelope with the name of the builder on. He was staying at the property whilst the work was going on, so was able to pass on the envelope. He rang me later in the day to ask how much the work was going to be and I told him and asked why and he said he was counting through the money. I was annoyed as the envelope was sealed and I counted the money more than once but brushed it off and forgot about it. Fast forward weeks later, dp off-handedly said he had taken the tip out of the money for the builder and kept it for his own. I am annoyed but he says he can't see the big deal (I refuse to believe he doesn't know this was wrong), he didn't give the money back to me or tell me at the time or ring me to ask. I am fuming, aibu?