Start by asking for everything, not just the obvious
When you adopt an adult dog whose earlier history is mostly unknown, request the fullest paper trail the rescue, shelter or previous keeper can produce, even if it arrives in fragments. Ask for any vaccination record and rabies certificate, paperwork confirming whether he is neutered, the microchip number and which registry holds it, the name of any previous veterinary practice, and any behaviour notes the kennel staff kept. A single vaccination card from one chapter of his life is still worth having, because it gives your own vet confirmed facts to build on instead of guesses.
Ask, too, about the things that rarely make it onto official forms. What food has he been eating, and how did he respond to it? Has he lived with children, cats or other dogs? Does he panic at fireworks, guard his bowl, or pull hard on the lead? Verbal answers count: write them down with who told you and in what context, so later you can tell the difference between a documented fact and a fosterer remembering her best impression of a dog she knew for three weeks.
Sort what you receive into confirmed, reported and unknown
Once home, lay the paperwork out and divide it honestly into three piles. Confirmed items are documents you can hand over: certificates, clinic printouts, chip details you have checked by scanning. Reported items are things you were told but cannot prove, such as an estimated age or a story about why he was surrendered. Unknowns are the real gaps: no record of dental work, no idea whether a lump was ever checked, no history before a certain rescue transfer.
That honest sorting matters because it shapes the first vet visit. Your vet can work with a declared unknown far better than with a confident guess that turns out to be wrong. If his age is an estimate, say so. If nobody knows whether he has reacted badly to an anaesthetic or a particular food, that uncertainty itself is useful information, and it belongs in his file from day one rather than surfacing during an emergency.
Fill the gaps with a fresh baseline at your own vet
Book a registration visit soon after adoption and bring the whole bundle, thin as it may be. A vet examining an adult dog with a patchy past will usually want to establish a baseline: weight, teeth, heart, joints, skin and coat, plus a check that the microchip scans and matches the number on your paperwork. If vaccination status cannot be confirmed from documents, ask how the clinic handles restarting or verifying protection rather than assuming cover that may not exist.
Use that visit to start the record you wish you had inherited. Note his weight, what you are feeding, any quirks you have already spotted, and the questions the examination raised. From here forward his history stops being a mystery and becomes a file you control, growing one accurate entry at a time.
Keep the bundle in one place from now on
Store the originals, scans of the paper copies, the chip number and your running notes together, and update the bundle after every appointment, booster or change of food. If he is ever boarded, walked by someone new or seen by an emergency clinic at night, that single packet answers their questions in minutes instead of relying on your memory under stress. Keeping it current with KinsLe's Pet Passport means his records travel as one tidy packet, so a new vet, boarder or helper starts from his real history rather than your best recollection.