Office workers can expect to spend £1,000 a year on things like teas and coffees, socialising and chipping in to whip-rounds for colleagues.
That includes everything from work clothing and stationery, to parties and nights out with colleagues, as well as coughing up for leaving gifts and charity requests.
That's £40,000 over the course of a 40-year working life - or around two years' salary after tax for the average office worker.
The calculation does not include the cost of lunches or travel to work, so if these were also taken into account the full cost would be even higher.
Here is how the annual average cost of working in an office adds up, according to the survey for Nationwide Current Accounts*:
* Clothes and bags, £119.16
* Drinks and nights out with colleagues, £102.24
* Christmas parties and dinners, £96.48
* Birthday cards and presents for colleagues, £66.60
* Coffees and teas, £66.36
* Sweets and treats, £64.32
* Technology (such as a tablet, phone, calculator), £58.32
* Leaving presents and cards for colleagues, £50.28
* Comfort items (such as tissues, tablets, anti-bacterial wipes and sprays) £49.68
* Colleagues' weddings, £47.04
* Charity/sponsorship requests, £44.64
* Births of colleagues' children, £43.92
* Secret Santa, £41.88
* Stationery, £41.04
* Other equipment (such as pens and highlighters), £38.04
* Retirements, £39.24
* Bereavements, £33.96
*Nationwide commissioned a survey of 2,000 office workers across the UK to make the findings.
Alan Oliver, Nationwide's head of external affairs, said: "Working in an office can be an expensive business, especially in big teams.
"While most people value the camaraderie of working in a team, birthdays, retirements and charity fundraisers can take their toll on our wallets and purses."