Glas Cymru has owned and operated Welsh Water since 2001
Welsh Water says it will take £22 off customers' bills to help ease the cost of water and sewerage services in the recession.
The annual bills of 1.2m customers will show the "dividend" as a discount.
The water utility claims it is the only one in the UK paying a dividend this year. Last year its dividend was £21.
Welsh Water is run by Glas Cymru, a not-for-profit company. It is proposing a capital investment programme of £1.5bn from 2010-2015.
The firm is preparing to send out annual bills from this week and has already indicated to Ofwat that it wanted average bills to be £376 for water and sewage services.
A Welsh Water spokesman said the average water bill next year will be £465.27. The figure does not include the £22 dividend.
Welsh Water finance director Chris Jones said: "This is the seventh and largest dividend made since Welsh Water came under the ownership of Glas Cymru, to be run solely for the benefit of our customers.
"We are pleased that we have been able to increase it and charge customers less than the maximum amount allowed by the industry regulator Ofwat.
"Efficiency continues to improve hand-in-hand with cost reductions, so we can finance our current £1.4 billion investment more cheaply and return benefits to customers via the 'dividend.'"
However, customers who pay for only one service, either water or sewerage, will have a dividend of £11, not £22.