Prosecutors are expected to announce on Wednesday whether Conservative politicians or officials will face charges for breaches of expenses rules.
The CPS is considering files sent by police following investigations in up to 27 constituencies.
It relates to claims some campaigning costs in the 2015 general election were wrongly recorded.
The Conservative Party has insisted administrative errors were to blame rather than any intention to deceive.
And it has said some of the spending was correctly declared.
It is alleged the Conservatives spent tens of thousands of pounds on local campaigns – including on “battle bus” visits by activists – which were either not declared or were wrongly registered as national spending.
The allegations came to light following an investigation by Channel 4 News.
Under complex election spending rules, parties must disclose national spending separately from money used to promote each candidate, and separate national and local limits apply.
Up to 16 police forces across England have submitted files to be considered by prosecutors.
The CPS will consider whether there is sufficient evidence of a breach in the law, and whether a prosecution is “in the public interest”.
If general election candidates are prosecuted the Conservative Party will have to decide whether to suspend them and replace them as nominees.
The last date for candidates to register for the election is 11 May.
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