---

@Just-Lisa-Now- wrote:

Hopefully the IRS will come out with a look-up tool online that we can use, but so far, no word about that.

---

Assuming the IRS creates such a thing (I expect that they will), that would have worked fine in the vast majority of cases for "round 1" EIPs.  But the early filers may be filing tax returns before their checks/debit cards have been issued for round 2.  So then we're branching off into a multitude of possibilities: delay filing, file and hope (and possibly amend later), file and claim the additional credit (and possibly deal with an IRS adjustment later), etc.