This could be attributed to my not RTFM, but for the benefit for all the others that do not RTFM… I got hit with negative interest charges because I simply tried to replicate some suggestions from the forum without actually reading through the docs more thoroughly - which I would recommend all of you do before using IBKR, as things seem to change frequently with this information.
Learning 1: Interactive Brokers always has a withdrawal hold period for your money
Learning 2: Interactive Brokers has negative interest rates for assets held in EUR of any amount > 50K EUR
Therefore, here is what needs to be done to avoid fees and interest:
Step 1:
Wire 450K USD (or whatever you need to move to Portugal) into IB account - no need to split this up as there is no negative interest for any amount in USD. This also helps because it starts the 3 day withdrawal hold clock on the entire 450K from day 1.
If you choose to ACH your money, the hold period below is 4 days, but could also be 44 days (unclear from docs as it says it is 44 days if you ACH it out to a bank different from the one it came from - not sure if SEPA transfer has the same limitation). Also, ACH has to be done in 100K chunks every 7 days.
Step 2: VERY IMPORTANT:
Wait 3 business days if wired, or 4 (or 44?) business days if ACH (there is a hold on that money even if the money is available to trade) - the hold means even though you can trade with it, you cannot move the money out of IB for 3 days - so DO NOT convert it to EUR before the 3 day hold period is done
Step 3:
Convert the whole amount into Euros (or in smaller chunks if you want to rate average across days).
Step 4:
Transfer whatever is converted via SEPA to your bank in Portugal immediately. It will only get there 3-4 days later, due to 2 days of your currency trade settlement time and 1 day of SEPA. However, there will be no negative interest charge for that time.
Some of the prior posts tell you to:
Move in 100K chunks of USD, convert and move - that due to this hold period issue would take two weeks to move about 400K. Also, if you convert as soon as the money arrives, you will pay interest for 3 days till you can move it out (unfortunately, I speak from experience here). Most importantly, at some point the limits may have been 100K - but now there is negative interest from 50K on.
So move all the USD there, cure it for 3 days, then convert upto the entire amount and move the EUR out in one day, and repeat if you did not convert the whole amount to get a different rate the next day.