AN OVERVIEW:
It is important to accurately and completely report international travel dates, as accurately and completely as possible. Any failure to do so can be problematic. Not every minor failure to do so will be problematic, but it can be. Omissions and multiple inaccuracies tend to be more problematic. How problematic will vary and depend on many factors. Apart from and in addition to the nature and extent of discrepancies indicated (a factor which can range from minor concern to a big concern), the big factors tend to be:
(1) how close-to-the-minimum presence the applicant is -- or how much of a margin over the minimum the applicant has -- more margin tends to be better (but a big margin is not always enough)
(2) the extent to which it is well-apparent the applicant is fully settled and living a life in Canada, and has been during the period of time reported to have been present in Canada
(3) applicant credibility; while any perception of overt intent to deceive tends to be highly problematic, the obvious, additionally any circumstances suggesting the applicant is not a reliable reporter of facts will tend to compromise the applicant's credibility, and this is a huge factor; for context, numerous or big errors in reported facts suggests a lack of reliable reporting, no matter how innocent or accidental, since it indicates the individual cannot be relied upon to provide accurate information, as evidenced by the applicant's failure to provide accurate information
RELIABLE SOURCES:
Government and other sources can help a lot to reconstruct the travel dates, BUT there is really only one source who can for sure provide a complete and accurate record: that is the PR himself or herself.
The PR is the one and only source in the whole world who can FOR SURE account for all cross-border events. The PR was there, each and every time.
If, as things turn out, the one best source of this information fails to provide a complete and accurate accounting of all travel abroad, IRCC has good reason to not just have questions but to be skeptical. Thus, in every case IRCC will at least make some effort to verify the applicant's information, and in some cases IRCC makes a concerted effort to verify the applicant's information.
Make no mistake: IRCC does NOT reconstruct an applicant's accounting of travel history. IRCC will consider various sources of information to determine if the applicant's account of travel history is accurate and complete. If IRCC determines the applicant's account is NOT accurate or NOT complete, IRCC will assess the significance of this against the application as a whole. Some report NO problem despite a three-week omission in their reported travel history. Others report RQ and even a highly skeptical response apparently triggered by what might seem to be an isolated and very small discrepancy in reported travel history. I referenced key factors above. Applicant's demeanor in the interview can make a difference. Collateral information can play a role.
But the overriding element is whether or not IRCC believes the applicant has, but for this or that mistake, provided reliable information which sufficiently shows the applicant met the physical presence requirement. To be clear: IRCC depends on the applicant to provide reliable information which sufficiently shows the physical presence requirement was met.
Thus, the report by
@scylla is an important one:
My advice is to keep track of everything on a spreadsheet yourself and list everything in the citizenship application - even if it doesn't appear in any official government records you can access. My husband (American) forgot about a single day trip to the US (i.e. same day return) where he crossed over and then back in a friend's car. He was keeping an excel spreadsheet listing all of this travel specifically for his citizenship application but forgot about this one. It also did not appear in CBSA records or through FOIA. But guess what? Somehow CIC knew about it all the same (they knew about the departure but had no record of his return). He ended up getting RQ'd because this trip wasn't listed in his citizenship application.
The reason I like this post is simple: it illustrates how and why the failure to accurately and completely report all travel history can cause problems. It also illustrates that the government sources cannot be relied upon exclusively (which should be obvious but for some reason perceptions otherwise continue to persist . . . one might consider, for example, a visit to the Haskell Free Library in Stanstead, Quebec to do some research on the subject about how easily one could exit the library into Vermont, and depending on how closely the video monitors are being in fact watched, continue down the road to Burlington or even New York City without interdiction by roving U.S. Border Patrol . . . and later return to Canada via the same route . . . just one among many, many places it is easy to walk or take a small boat across the border without passing through border security).
I say the report by
@scylla is important notwithstanding this particular example (RQ triggered by omission of one short trip abroad) is probably unusual. My sense is that an isolated, single omission will NOT typically trigger RQ. IRCC is well-acquainted with the fact that many if not most applicants, if not nearly all applicants, make some mistakes in their application, including as to reported travel history. So long as the mistakes are minor (noting that almost any omission of a cross-border travel event is significant, but in context can be minor, as in not having much impact on the overall assessment), few in number, and do not implicate
EITHER (1) the
POSSIBILITY of not meeting a qualification requirement
OR (2) compromised applicant credibility, THEN the mistake(s) are not likely to trigger non-routine processing let alone pose a risk to the outcome of the application.
BUT, as the
@scylla example illustrates: an accurate and complete accounting of travel history is IMPORTANT and any discrepancy can trigger elevated scrutiny.
How much leeway there is, otherwise, varies. It depends. It depends on many factors. It is very difficult to forecast.
For me it is impossible to give all dates for last five years considering my health and state of memory. Can I request my learned friends if they can suggest how should I proceed.to get these dates as accurately as possible.
The question may be how close you can come to reporting all trips accurately.
Combining what you can confirm from both the U.S. records AND CBSA travel history, in conjunction with using every other resource available (email, credit card transaction dates, banking transaction dates, family memory as well as your own, anything and everything which can help you reconstruct the trips), you can probably come very close to being near accurate.
Will that be enough? Whether that will be sufficient to avoid something like RQ, that too will DEPEND on multiple factors. Whether that will be sufficient to assure a positive outcome, that too will DEPEND on multiple factors.
No one here can fully unravel all the relevant considerations and give you assurances about how this will go. The best assurance, the best insurance, is to be sure to get every travel date correct. As
@scylla suggests, the best assurance is a completely accurate accounting (such as in a spreadsheet) of each and every trip. And again, there is only one best source for the information populating that spreadsheet: the PR himself or herself.
You could wait to apply only after you are sure you can account for all trips accurately. You probably should wait to apply only after you are confident you can be very near accurate in accounting for very near all trips. You almost certainly should wait to apply only after you are confident you have a substantial margin over the minimum . . . the less certain you are about reporting ALL travel dates accurately, the BIGGER your margin should be before you apply.
BUT again, a big margin does not always suffice . . . your credibility looms very large, and how accurately your accounting of travel dates is can have a huge impact on your credibility. In this regard, it warrants noting and emphasizing that in order to deny an application (let alone subject it to non-routine processing and a referral to a Citizenship Judge for a hearing) IRCC does not need to show or even conclude the applicant's errors add up to enough days to show falling short of the minimum; the question is whether the applicant's accounting of presence meets the burden of proving presence. Thus, for example, just because IRCC only identifies the applicant missed reporting two or three trips adding up to another thirty days abroad, that does not mean it will go OK if the applicant had a margin above the minimum by more than thirty days or even a hundred days. Once the applicant's accounting is in doubt, it is subject to being doubted in its entirety.
Whether the government records will provide enough information to give you such confidence about your travel history is something no one here can answer.