Well I don't know how Canada does it but for most of the west, every bank must maintain a certain amount of reserves. The US Fed lowered that in 2020 and has not raised it yet.
If they lend out so much that they don't have enough reserves, they can overnight borrow from other banks to meet reserve requirements. The overnight lending rate is what the banks pay to other banks for that loan. This is simplified but mostly correct.
The Fed sets that overnight lending rate. Because it costs more to loan overnight, if a bank is low on reserves it will need to charge higher interest for loans to consumers that it lent to when going under reserve requirements.
Of course, this is assuming they went under reserve requirements and need to do this at all. If they didn't, then they can lend their excess cash to other banks and get the Fed Fund rate as interest.
Thing is, most banks have a ton of reserves due to the printing press and those M1/M2 numbers. But we don't have to guess that, we can look - keep in mind minimum reserve requirements were lowered in 2020, so not only have reserves gone way, way, way up - they also aren't required to keep as much.
So, banks are awash in money basically.
If you take the 3 charts, M1, M2, and bank reserves, the problem is clear. The entire system is awash in money. Not just a little bit, 40% added to M2, 500% on M1, and banks have 200% more reserves than they had in 2019.
This is why we have so much inflation.
View attachment 257015