TSB will be valued at between £1.1 billion and £1.45 billion when Lloyds Banking Group sells a 25% stake in the bank later this month.
Announcing further details of the long-awaited stock market flotation, Lloyds said that TSB shares will be priced between 220p and 290p, giving the challenger bank a mid-point valuation of £1.275 billion.
That compares with the £750 million that the Co-op agreed to pay for the branches before the discovery of a £1.5 billion hole in the mutual's balance sheet caused the deal to collapse in April 2013.
The final pricing for the offer will be announced on around June 20, when conditional dealings in the shares will also get under way. TSB has 631 branches and is being offloaded by Lloyds in order to meet EU rules on state aid following the group's rescue at the height of the financial crisis.
Lloyds, which also includes Halifax and Bank of Scotland, is still 25% owned by the taxpayer. Its shares opened lower today as the announcement of the price range valued TSB at below the £1.5 billion reportedly on the books of Lloyds.
The pricing range reflects caution following the recent disappointing performance of other stock market flotations, with over 50s insurance and holidays group Saga among those to have seen shares decline.
TSB stock will be made available to institutional investors as well as intermediaries selling to ordinary retail shareholders.
The retail offering contains an incentive allowing each retail investor to receive one free share for every 20 shares acquired, up to the value of £2,000, and held for a year after the float.
TSB, which has 4.5 million customers, is the seventh largest retail banking group in the UK. It is aiming to become a larger player in the current account market, growing from 4.2% to 6% over the next four to five years.
In its prospectus for potential investors, TSB said it did not expect to pay a dividend until the 2017 financial year. It reported profits of £172 million for 2013 and a figure of £60 million for the first three months of 2014.
The bank last week announced that staff are to be handed free shares worth £100 as part of a John Lewis-style reward scheme.
As newly-created TSB Partners, 8,600 employees from the chief executive to front-line branch workers will also be in line for an annual performance-related award that could pay a maximum 15% of salary.
Chief executive Paul Pester, whose basic salary will increase from £600,000 to £700,000 a year, will be entitled to a maximum potential award of £1.68 million - the equivalent to 65 times the current average pay of non-managerial TSB staff.