I live in Canada and work in the USA. Most of the time, I took day trips to the USA (no absence accrued), but for several months I spent whole work weeks in the USA, returning to Canada for the weekend. Although I received an RQ, I did become a citizen under the 3/4 rules (from application to oath took two years). You will have to provide ample data to show that you actually lived in, and your life was centred in, Canada. (See below for my recommendations on meeting RQ requirements.)
File your taxes, if you are required to do so. (If you earn income in the USA, you are likely required to file taxes in BOTH countries, though you probably won't have to pay Canadian income taxes.)
It is not true that if you are in Canada any part of a day, it counts toward citizenship. If you leave and return to Canada on the same day (all before midnight), that is a day trip, and it does not count as an absence. But if you are not in Canada at midnight, that is a day's absence. For example, if you leave at 11:59 PM on Monday and return at 12:01 AM on Tuesday -- a trip of only two minutes, you have accrued one day's absence because you were not in Canada at midnight.
Suggestions for Meeting RQ Requirements:
1. Use a credit/debit card for all spending in Canada and keep all bank statements, so you can show the kind of spending activity that establishes a life lived in Canada (groceries, restaurants, etc.) Also keep receipts for cash purchases. (Do not use Canadian credit/debit cards in the USA -- providing bank statements with lots of USA purchases detracts from establishing a life centred in Canada. Get US credit/debit cards, if you don't already have them.)
2. Keep all leases, proof of each rental/mortgage payment, copies of all utility and phone bills.
3. Register and insure your car in Canada.
4. File Canadian taxes as a resident of Canada; and file U.S. taxes as a resident of Canada. On all forms, for both governments, maintain that you are a resident of Canada (remember, the countries now share more and more information).
5. Use an RFID card to enter the USA (US Passport Card or NEXUS), so you can flash the card at the machine before driving to the booth -- this will establish a record of every trip into the USA (sometimes border guards don't swipe your passport on their machine, with an RFID card, you can take responsibility for that -- you want both the CBP and CBSA border entry reports to be as accurate as possible). (Get a copy of both of these reports BEFORE submitting your citizenship application.)
6. Keep meticulous records of each and every trip across the border. Listing should include: i) date left; ii) date returned; iii) country visited; iv) purpose of trip (e.g., business, pleasure); v) total absence from Canada; vi) total days in the USA (if you are a US Tax Person, you need to keep track of every day spent in the USA -- each day you are in the USA for any amount of time is considered a "day present" -- because some tax consequences are based on the number of days present in the USA.)
