You already know the split week runs on handoffs. The kids move from your house to his, the car moves with them, and somewhere in the middle a permission slip goes missing. The fix most families try first is a group text that everyone reads and nobody answers. What works is a single handoff note, written once a week, by one person, in the same spot every time.
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Name the writer before you name the note
Decide who writes the Sunday note before you decide what goes in it. In most split weeks, the person whose row is ending that day writes it, because they know what happened. If you share the job, agree on which Sunday belongs to whom. Shared authorship sounds fair and usually ends with two half notes and no line about the dentist.
Check that the writer can reach the other house by the time the note is due. If the note goes out while the other parent is driving, it will be read at the next red light, which means it needs to be short.
Keep it to five lines
A handoff note that reads like a report will be skipped by Wednesday. Five lines covers most weeks: what each kid needs from the next house, anything due in the coming days, who is picking up what and when, any change to the usual routine, and one thing that is going well so the note doesn't read as all alarm. Add lines only when a rule changes for the week.
Set one check-in, not a stream
Pick one midweek moment, a quick call or a two-line reply, where the other house confirms the note landed. This is the part families skip, and it is the part that tells you the note is working. If nobody answers on Wednesday, you have learned something useful about the week, and you can fix it without a fight.
What to check at the end of a month
Read the last four notes back to back. Look for the same problem appearing twice, such as a lunch that always gets forgotten, and move it into the standing routine so it stops needing a note. A good note eventually gets shorter, because the family has absorbed what used to need explaining. If yours keeps getting longer, the week needs a structural change, not more sentences.
For a wider look at how the two rows fit together, the Kids' Week and Mom's Week page lays out the basic frame.