Is police clearance needed while you apply for citizenship?
Only if you have spent a cumulative 183 days in a single country in the last 4 years from your application date. If so, you need a PCC from each country that it applies.
For clarification:
Applicants are instructed to submit a Police Clearance
WITH THE APPLICATION if the applicant has "
spent a cumulative 183 days in a single country in the last 4 years from your application date."
Additionally, later in the process IRCC MAY request Police Clearances from an applicant even if the applicant did not spend that many days in a country.
This is NOT common. But it is clear IRCC can. And there are multiple reports that IRCC has done so.
Such a request would be very unusual unless:
(1) the applicant has extensive time and ties in the country, OR
(2) IRCC otherwise has information suggesting there might be a criminal charge in that country.
Even for applicants with extensive time in another country, but less than six months total, it appears to be unusual for IRCC to ask for a police clearance. Nonetheless, a couple recent anecdotal reports in the forum illustrate an example of the first of these instances in which IRCC might ask for a police certificate (despite spending LESS than 183 days in the other country): applicants who waited to apply so that they had been in the other country just a little less than 183 days total, who then were later (after the interview, if I recall correctly) asked to submit police certificates.
REMINDER: the actual qualifying requirement underlying this is that the applicant have NO PROHIBITIONS, and in particular this is about the prohibitions arising from pending foreign charges or foreign convictions within four years before applying. That is, the reason some applicants must submit police certificates is to meet their burden of proving NO prohibitions based on charges or convictions in any country outside Canada (there is also a prohibition for indictable offences in Canada).