A FRSB spokeswoman said the discount was available immediately. It will apply to charities that want to join the FRSB for the first time and to existing members.
Discounted annual FRSB membership fees range from £15 for organisations with voluntary incomes of less than £10,000 to £135 for those with incomes of up to £1m.
Membership of the Small Charities Coalition is free, but is open only to charities with incomes of less than £1m a year.
Recent figures showed that growth rate of FRSB membership was slowing, with the membership increasing by 90 in the year to December 2012, compared with 118 the previous year. The FRSB now has 1,501 members.
In his report last year on the Charities Act 2006, Lord Hodgson said membership levels were the FRSB’s greatest weakness.
The FRSB spokeswoman said the discount was part of a "generic push" to help ensure that self-regulation was as accessible as possible for all parts of the sector.
"The FRSB is always keen to do what we can to make fees for self-regulation as attractive as possible," she said. "We’re always looking to do something like this where we can."