A recall petition for a Conservative MP convicted for a false expenses claim will open on 9 May.
Chris Davies tried to split the cost of photographs between two office budgets by faking invoices, when he could have claimed the amount by other means.
Voters in Brecon and Radnorshire will have six weeks to sign the petition in six locations across the constituency.
If 5,303 eligible voters sign it, 10% of the electorate, a by-election will be held.
House of Commons speaker John Bercow confirmed the recall petition on Wednesday, after Mr Davies was given a community order of 50 hours unpaid work and a £1,500 fine, at Southwark Crown Court, the previous day.
People registered for postal votes will receive a signing sheet to return if they want to sign the petition.