With the help of diagrams, workers are shown how to open the door using their hand, and are requested not to leave toilet roll on the door handle.
The instructions, put up in Lloyds Bank's Old Broad Street office in central London, give full instructions of British etiquette in the lavatory, including 'The sinks are for washing your hands only - no using hand towels or toilet paper as a plug'.
The instructions are there for workers from around the world with different toilet habits. For example in south America, it is common to put used toilet roll into a bin beside the loo because few houses have sophisticated drains that can cope with loo roll.
And in continental Europe, squatting over a 'hole-in-the-ground' toilet has been the norm until very recently.
The poster has gone up in several Lloyds Bank offices, and a spokesman said today: 'We take the health and safety of our colleagues very seriously.'
The high street bank is just the latest business to acknowledge the different toilet habits of workers from overseas - factories across the country are reportedly putting up posters detailing British loo etiquette as more workers arrive from overseas.
Last week MailOnline reported how a DHL warehouse in Swindon had installed a European-style 'hole in the ground' loo because foreign workers kept breaking the English-style loo seat by standing on it.
When managers at the depot, a distribution centre for B&Q, realised that their employees from Eastern Europe preferred squatting while going to the loo, they ordered a toilet to match their requirements.
A source said the new loo was installed after instructions telling staff how to use an English loo went ignored, saying: 'Staff were fed up with the toilet seats breaking and workers leaving a mess.'
But British-style loos are comparatively rare in some countries including India and Japan, where they were only introduced recently.
However, squat loos may be set to gain in popularity in Britain, thanks to doctors who claim that the squatting posture brings health benefits.
Some medics believe that squatting while going to the toilet is a more 'natural' position, and could protect against disease.