Subject: Re: SOLD : $423.25
I bought May 30 T-bills at 98.655"

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Is that the net price you got? Because I bought some May 30 T-bills today at auction and they were 96.6717 which results in a stated rate of 5.255% and an investment (annualized) rate of 5.400%.
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Price: $98.671653

[I presume you mistyped and your price was 98.xxx from lower in your message, not 96.xxx]

Yes, 98.655 was the net price I paid. Plus a small commission which brought it up to (ummm) 98.657 all in.
That was in the secondary market. I can't bid at Treasury Direct, you have to be a "US Person" to do that.

If your price was the 98.671653 auction price, that's only an annualized yield difference of about 0.066%/yr from my trade. Prices are almost flat, but not perfectly so.

Jim