The authority needs to find another £24m of savings over three years, starting from April 2017.
This is on top of £86m of savings that have already been made in the last six years.
People can have their say by attending a public meeting tonight at the Guildhall between 7pm and 9pm.
Council leader Cllr Donna Jones said: ‘This year’s budget consultation is slightly different to previous years as we want to understand how residents feel about the ways we’ve been working and managing our budget.
‘Last year, 2,500 people got involved and told us what they thought and we took that feedback on board when making decisions.
‘We want to hear from you again this year – it’s your council and your opinions really do matter so please get involved and have your say.’
The consultation runs until Monday, October 31, and is available at portsmouth.gov.uk/budget-consultation