Refuse the two-notebook problem from the start
Shared dogs drift into trouble through duplicated records. One home keeps a diary, the other relies on texts, and within a month neither side can say with certainty what the dog ate yesterday, whether his ears were checked, or which home booked the booster. Agree instead on a single log that both households treat as the only truth, with one shared place for it and a shared understanding that if it is not written there, it did not happen. That sounds strict, but it protects the dog from the classic shared-care errors: a double meal on changeover day, a missed regular care item because each home assumed the other had done it, and a symptom mentioned in a doorway and forgotten by both sides.
Log the day-to-day, not just the dramas
A joint log earns its keep on ordinary days. Record feedings with amounts, walks and roughly how far, toilet notes when they change, appetite, mood, sleep, and any regular care given, in the same short format in both homes. Ordinary entries create the baseline that makes a real change visible: the home receiving him on Friday can see he ate lightly all week rather than hearing he seemed fine. Keep entries factual and brief, observations rather than verdicts, and write them the same day. Include upcoming appointments and who is taking him, plus the outcome afterwards, because the home that missed the vet visit still needs the vet's instructions in full, not a summary retold from memory.
Make the handover note a fixed ritual
The riskiest moment in shared care is the doorstep swap. Build a short handover entry into every changeover, written by the home he is leaving: when he last ate and how much, when he last went out, how he has seemed today, anything unusual in the log this stay, and what falls due during the next stay, such as a grooming appointment or the end of a food bag. The receiving home reads it before the door closes, while questions can still be asked face to face. Bags, food, lead, and any current care items travel with a note of what is running low, so neither home discovers an empty tub on a Sunday night.
Settle disagreements in the log, not around it
Two homes will sometimes do things differently, different walk routes, different treat habits, slightly different house rules, and a shared log surfaces those differences kindly and early. Use it to agree the essentials in writing: the food and amount, the cues used, what is off limits, and how each home records a concern. If one side notices a recurring problem, the log's dates make the conversation factual rather than accusatory. Agree also who can authorise a vet visit and who covers which costs, and write that down in the log before an urgent day forces the question under pressure. Family Sharing through KinsLe gives the relatives you pick in each home access to his profile, whichever roof he is sleeping under that week.