對於這個問題我也是挺好奇的，再加上沒人解答我的推文，就寫了信問TD客服
先說結論，後面再附上原文
1.目前的利率為0.35%
2.自從2021年7月起，沒有美國實際地址的人，不再有替代現金的轉存服務
(Cash alternatives)，也就是你查到的現金轉去MMF
3.原文後段有提到SIPC的相關保障
With respect to your inquiry, the redemption and purchase transactions you
are seeing are what are called a "sweep" transactions. These transactions are
simply related to Money Market Purchase and redemption/flow of funds through
sub-accounts. In your case these funds were being swept to an from the FDIC
insured cash sweep account, also known as the IDA (insured deposit account).
However, as of July 2021, clients who do not have a U.S. or U.S. Territory
physical address cannot be enrolled in the IDA (Insured Deposit Account) Sweep
Impacted accounts, such as your own, are now enrolled in "TD
Ameritrade Cash". We also sent you notification of this change at this time
as well. This means that deposits of cash into your brokerage account will
remain in the account and earn interest paid by TD Ameritrade. This is called
the TD Ameritrade Cash feature. This is why you no longer see those sweep
transactions anymore.
While both cash features currently pay 0.35%, there are some minor
differences in how interest is paid and when interest begins accruing. Both
the IDA and the TD Ameritrade Cash Feature pays accrued interest on the last
business day of each month. In some instances, accrued interest will be paid
earlier in the month for clients in the IDA. Additionally, cash deposits
into the TD Ameritrade Cash Feature begin accruing interest on the date of
deposit while interest does not begin accruing for deposits into the IDA
until the next trading day.
As a result of your cash feature changing from the IDA feature to the TD
Ameritrade Cash feature, your cash balance will no longer be insured by the
Federal Deposit Insurance Corporation ("FDIC"). Instead, the cash balances
in your brokerage account will be eligible for coverage by the Securities
Investor Protection Corporation ("SIPC") of which TD Ameritrade is a member.
SIPC protects the assets of its members' clients up to $500,000, including up
to $250,000 for claims for cash, including your TD Ameritrade Cash feature
balances. Additional information about SIPC is available at www.sipc.org.
Additionally, TD Ameritrade provides each client $149.5 million worth of
protection for securities and $2 million of protection for cash through
supplemental coverage provided by London insurers, up to the aggregate policy
limit of $500 million.
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