Building the sheet so the next due date finds you
Keep the spreadsheet deliberately plain: one tab for vaccinations, with columns for the component given, the date of the visit, the next due date, the clinic, and a notes column. Plain matters because a sheet with clever extras is a sheet your partner will avoid opening. Sort by next due date and freeze the header row, so the top line is always the next thing this cat needs.
Add a small status column with only three values you both use the same way: booked, done, and check. When a due date is within two months, its status becomes check until one of you books, then booked until the visit happens. That tiny shared language prevents the classic shared-system failure where each partner assumes the other has handled it.
Sharing rules that keep one version true
Agree that there is exactly one spreadsheet, stored in the shared drive you both already use, and that neither of you keeps a private copy. Private copies drift, and the day they disagree you will trust the wrong one. Name the file with the cat's name in it, so it surfaces when either of you searches for anything about the cat.
Settle who updates what: the person who attends the appointment enters the new dates before the end of that day, from the certificate, not from memory. The other partner's job is the monthly glance — open the sheet once a month, look at the top three rows, and raise anything due soon in ordinary conversation rather than assuming it is in hand.
Using the notes column for what dates cannot say
The notes column earns its place at vaccination visits. Record how your cat reacted afterwards — quiet for an evening, off food for a day, completely unbothered — and anything the vet flagged for next time, such as weight to watch or teeth to recheck alongside the booster. When the next appointment is booked, those notes tell whoever is taking the cat what to mention, without a handover conversation that may not happen.
If your cat sees a different clinic for any reason, note which clinic holds which record in the same row. Split records across clinics are common and harmless, provided one place — this sheet — lists where everything lives.
Reviewing the sheet together, briefly and regularly
Twice a year, spend ten minutes together reading the sheet against the paper or digital certificates and correcting it. Check especially for components with different due dates, which are the rows most often merged or mistyped, and for any row still marked check long after its date has passed.
Protect the sheet from helpful tidying. Lock or protect the header row and the formulas, if you use any for highlighting dates that are close, so a partner sorting or filtering does not quietly rearrange a column out of alignment with the rest. One scrambled sort can attach the wrong due date to the wrong vaccine, and the error looks authoritative precisely because it sits in a tidy spreadsheet.
That same discipline pairs well with KinsLe Family Sharing, where relatives you pick get profile access for your cat while the vaccination rows themselves stay in the sheet you and your partner maintain.