POST offices are to start offering personal loans and credit cards as part of the "sweeping commercialisation" of the network.
Unsecured loans will be offered across the country from October, in direct competition with banks and supermarkets.
Changes to opening hours were also announced which will allow post offices to open in the evenings and on Sundays.
Sub-postmasters will decide on opening hours under new flexibility arrangements aimed at generating more income and cutting the Royal Mail's losses, which are running at £750,000 a day.
Royal Mail chairman Allan Leighton announced the range of financial services during a speech to the annual conference in Scarborough of the National Federation of SubPostmasters.
He said the "reinvention" of the post office was now under way based on the entrepreneurial skills of sub-postmasters, backed by new products and incentives.
"We are determined to put our post office branches on a better financial footing by giving customers the products they want and letting sub-postmasters get on with the job of running their branches to suit their customers.
"Post office branches will offer additional financial services in the way that supermarkets currently do but they will be more accessible, offered with a more personal touch and backed with a real community brand."
Customers will also be able to take out a post office credit card or buy motor and life insurance.
The number of branches selling euros and US dollars will increase by 300 from next month and an extra 1,000 branches will sell Moneygrams from later this month.
Mr Leighton said sub-postmasters will be given a greater incentive to make money and will increase their profits every time they make an extra sale.
There are more than 17,000 post office branches across the country, although the number in urban areas is being reduced by an estimated 3,000 over the next 18 months as part of the Royal Mail's drive to cut costs
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