Client: Re: Bill XXXXX from YYYYY is due. This has been paid, maybe you should check your bank account before sending this!
Me: Sorry for any confusion, as I previously emailed we have moved to a new automated system this month. I’ll look into it.
This system takes a feed directly from our bank and automatically sends reminder emails when invoices are overdue.
I have double-checked our bank just now and the system is correct. This invoice has not been paid.
So not only has this client not paid me, but he also tried to make me feel bad about it.