Download of tax slisp

So, the filing deadline for T3 returns and slips is May 1, meaning slips will be trickling in for the first half of May. But, T1 returns are still due by April 30. Anyone else see a disconnect here?
Yes, I know, monthly investment statements show monthly income & capital transactions. I also know that these statements routinely refer to income as either a distribution or a dividend. These terms are used very loosely since the investment broker doesn’t know the nature of the payments until slips are issued by the various funds. Well, I’ll file with what I have and advise clients to check their mail often. And, I’m not doing adjustments for free.

when i receive their tax files, i email to advise cra issues with uploads and responsibility on them to ensure I have all slips - if not possible, interest and penalties on noa or a fee for refiling the return,
this is crazy

The interest should be around $200.

Yes, have 3 clients with duplicate T4s. Called CRA, they say employer error… client called employer> says slips were issued as amended.