Only existing Prospect members can become retired members, so the standard "How to join" below the next paragraph does not apply. To join the RMG, a member needs to have been a working member up to retirement, and (barring exceptional circumstances) needs to apply for retired membership within 6 months of retirement.
Retired Members who subsequently take up employment are strongly advised to contact the Prospect membership department about becoming a working member for the duration of that employment.
How to join
Just go to Prospect's national 'join us' page http://www.prospect.org.uk/joinus/index.
You will be asked to select your employer from a drop-down list, then you can check the current subscription rates, and either join online or download a PDF version of our application form.