Outside of using Lunar banks on Jupiter, or other pretty optional things, where exactly is it going to take hours to contact a bank?

I'd imagine financial transactions are pretty easy to do with QE comm. They don't have a very large file size, so while QE comm bandwidth is expensive, that's a really cheap use. Simply tacking it onto the transaction as a processing fee seems easy to do. Beyond that, I'd imagine most of the inner system is pretty connected banking-wise so simply bringing along financial data with the rest of the egocast packet seems easy enough. A system pretty similar to the way modern debit/credit cards should work. Money is deducted from the account holder (which can be done locally), but isn't transferred to the merchant until a typically daily check in with the bank. This isn't done locally in the present day, but it should be possible to make such a system to beat out light-lagged banking. Using less back of the envelope math (wolfram alpha) the maximum distance between earth and venus is about 14 light minutes, while the maximum Martian distance (from earth) is about 24 minutes. Straight line distance between planets seems ok to use, as a lot of that will be neutrino comms, it will be a little longer for laser or radio link. If you have some of the preliminary parts of the financial transaction done locally to avoid keeping people waiting it seems pretty doable. There is a hacking risk here (that someone could locally change the amount of money in their account, pay for something, and make off with it before the transaction clears), but I imagine that interplanetary banking is pretty well insured (one thing the PC is very good for), and the law has pretty long arms in the inner system, so this vulnerability doesn't seem critical. In most of the outer system, where the distances become unbearably long money isn't used much, so that's not a problem. (A potential reason for rep systems to work better out there). That's why I brought up Jupiter from the inner system, it's far away, and banking might be harder thanks to the security conscious JR. The maximum Earth-Jupiter distance is about 54 minutes, so a nearby 2 hour time for each stage of the transaction to clear seems like more of a problem. I'd guess most banking between the inner and outer system is either done by a few well insured banks, or mostly done with QE comms. I don't know a whole lot about how exactly electronic banking works though, so everything here might be pretty off base. So in the end I think banknotes are back, in the form of well encrypted local banking info to speed up transactions for the convenience of the buyer. I suspect there are a few potential campaign hooks hidden here. Perhaps a hacker is cracking local encryption on people's wallets, which might require skills or equipment beyond the norm (maybe an async hacker, or someone using TITAN built computronium as a decryption machine). Maybe just someone trying to destabilize inner system economies. For banking as a whole, I could see using QE comms or similar quantum tricks to try to send trading info slightly into the past, for Retroactive High Frequency Trading, which should set off Firewall's red alerts pretty hard.

One thing to consider is that you don't necessarily need real-time transactions that frequently. Most banks probably have branches or sister entities on most habitats, and even if they update according to the limitations of light speed the funds are still going to transfer as quickly as you do. In addition, the likely issues are pretty easily dealt with. There's a marginal chance that someone will fork themselves and spend the full amount of their bank account balance in multiple places at the same time, and that sort of thing already has analogous comparisons IRL with things like checks. Basically, you can't outrun the flow of money, and if you needed to pay money you don't yet have somewhere for some reason you would probably get instantaneous authorization from a local branch and suffer consequences after the fact if you spent more than you had.

Not to mention the fact that there's probably a handful of cryptographic physical currencies: lock your credits into a physical form for transfer. The security sucks, but it's good enough for transactions made in good faith: you'd probably have one-use codes with authorization, so you could theoretically double-up on credits with counterfeiting equipment, but whenever they were first transferred (which could be done automatically via PAN) the old physical forms would be obsoleted (out-of-date key) and the credits would be associated with a new one-time key. QE could be used in EP to facilitate this, but it'd be somewhat pricey for what you get. Coincidentally, this is not entirely dissimilar from the old-school checking account method, only with the potential for reuse of a credit unit (you could theoretically make a "coin" with the ability to have fluctuating value and near-infinite transfers).

I could see something like this working. It would be a memory chip with a cryptography circuit and a 'trusted authority' certificate to verify that the issuing authority is a valid one. On the chip would be something like a Bitcoin wallet containing the 'funds' issued as credits. The standard would have to be a universal one. What you'd do on the other end, however, is trade the cryptocoin to a bank or some other entity in exchange for local funds. They'd advance you the local funds as a loan, effectively, until the balance on the cryptocoin was verified with the issuing authority. (this is basically the way checks work now, except without the added security measures.)

Yes, we know about credsticks. However, there really aren't very many details about how credsticks *work* in Shadowrun. They "just do". This is about how something similar would work in Eclipse Phase, where the details matter for story reasons and plot hooks, extrapolated off of real world technologies.