What is Government Account Series?

 Go to: https://fiscaldata.treasury.gov/datasets/daily-treasury-statement/public-debt-transactions

and look up the lines:   Issues Nonmarketable Government Account Series and: Redemptions and Nonmarketable Government Account Series

The numbers are similar every day.  For 8/27/20, there were $414.07 billion issued and $414.24 redeemed.  For some reason, the Treasury issues and redeems about $400 billion of non-marketable debt every day.  That explains the $100 trillion+ of churn every year.

But why do they do this?  A one-day Treasury bill is just as good as cash.  So this is effectively an internal currency.  But still very mysterious.  Why wouldn't they use at least 7-day bills? The things to look for would be sudden changes and if this increases over time.

And indeed it is increasing over time, but not by much.  On 8/27/19, as a comparison, there was 380.5 issued and 373.8 of redeemed of Government Account Series.