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:
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
Convert the whole amount into Euros (or in smaller chunks if you want to rate average across days).
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.