> the math for $1499 interest is no different than $1501 interest.

This particular limit must be because once over $1,500 of interest, a Schedule B must be included with Form 1040, adding complexity they had to leave out of scope for now.

In general, the higher the AGI, the more complexity as various phase-outs start kicking in, requiring more forms or worksheets.

There are a couple of forms that you only have to file if your income is $200k or higher. 8959 (extra Medicare tax) and 8960 (net investment income tax) are examples. Child comments point out the schedule b for interest over $1500. So it higher income returns are more complicated.

I was thinking this too. Maybe it's just a way to safely limit damage if something went wrong with the system in these early trials...?

Seems obvious it's a way of capping the complexity of the filings. Have to draw lines somehow. Dollar amounts are pretty clear.

Because most audits are done on income over that level.

Also, this is definitely the "MVP" version of this, and I would venture people with incomes totaling more than 250K have at least one other thing "not supported yet" and it makes for an easy filter.