A friend runs her own business, which means she can claim all sorts of things against tax.
We always split the bill when we go out to eat, but she takes the receipt with her.
"Another one for the accountant", she says cheerily.
Am I wrong to feel affronted that she is making money out of me? I like her a great deal, but I'm retired and she is considerably better off.
I grew up in a trading household. Every day my brother and I would hear our mother shamelessly bullying a grown man on the other end of the phone, one she hardly knew, to sell her a consignment at the price she wanted to pay and not the one he wanted to charge.
It meant we learnt to chat openly about money, rather like other children easily pick up a second language from one of their parents.
However, it is peculiarly British to be deeply embarrassed and uncomfortable talking about our finances to others. Yet the only way you will possibly find out what your friend is up to when she swipes the receipt is to ask her.
I suggest you practise in front of a mirror until you have perfected the right mix of naivety and awe in posing the question: "When you give the receipt to your accountant, does he give you all the money back?"
She might be just collecting all her receipts and sending them off to be logged.
Or she might be falsely claiming you as a client she entertains on behalf of a business that uses her services.
It will be up to you to judge where the friendship lies when she responds.
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