People who do not have access to a bank account pay an extra £485 a year for everyday bills and services, research from an account provider suggests.
More than 1.2 million Britons do not have a bank account, so miss out on discounts reserved for those who pay bills by direct debit, said Pockit.
This ramps up the cost of energy bills, broadband and phone contracts, it said.
"For many of us, having a bank account is a basic fact of life," said Pockit boss Virraj Jatania.
"Yet the unbanked face a banking poverty premium which can put a real strain on their finances."
UK Finance, which represents the UK banking industry, said banks took their financial inclusion responsibilities "extremely seriously".
"The banking industry is committed to ensuring banking is accessible to all. There are over seven million basic bank accounts in the UK, helping customers across the country access vital banking services," it said.
Traditional banks can reject customers applying for accounts if they do not have enough forms of ID, or if their credit rating is poor.
But Pockit, which provides basic account services, said this meant many were being penalised.
It analysed prices from leading service providers and found:
- Energy and broadband providers offer discounts to customers if they pay by direct debit - a saving which is not available to those without a bank account.
- Mobile phone companies offer better deals to those paying via direct debit rather than pay-as-you go customers.
- Those without accounts have limited options when looking for credit, and often turn to expensive cash-in-hand "doorstep loans".
In one example, it found two of the UK's three largest broadband providers, BT and Virgin Media, offered a "super line rental discount" if you paid by direct debit.
But customers without a current account had to pay using methods such as cash transfers, costing them £38 more a year on average.
On electricity and gas, it analysed Ofgem data and found that those using pre-payment meters paid on average £141.57 more each year than those who paid by direct debit.