Your dog was clean for months. Now there is a small wet patch on a table leg, or on the corner of the sofa. Sometimes it is on a bag a visitor left by the door. The amount is small and the target is upright.
Marking and accidents are different problems
An accident is a full bladder emptied on the floor, usually flat ground, usually because your dog could not get outside in time. Marking is a small deposit aimed at something vertical, often something new in the house.
The two need different responses, so it is worth deciding which one you are looking at before you change anything. Amount, surface and timing tell you most of it.
Book the veterinary check first
Frequent small urinations are also what a urinary tract infection looks like, and a change in toileting is a behaviour change. Sudden behaviour change warrants a veterinary examination, and pain often shows up as a change in behaviour rather than as a limp.
Ask for a urine sample appointment. Getting that result back is faster than a month of training the wrong thing.
What to do today
Clean every past spot with an enzymatic cleaner made for urine. Ordinary household cleaner leaves the scent marker your dog is answering, and some contain ammonia, which reads as urine.
Close the doors to any room where marking has happened, for now. A dog cannot rehearse a behaviour in a room they are not in.
For the next 10 days, take your dog out on the leash for 5 quiet minutes every 2 hours. Feed 2 treats the moment they finish outdoors.
When a new bag, box or visitor's coat arrives, put it up off the floor. New objects at nose height are the most common trigger in the house.
Supervision, not punishment
If you catch your dog starting, say their name once and walk to the back door. You are interrupting and redirecting, not correcting.
Punishment-based approaches are associated with fear, avoidance and defensive aggression, and reward-based methods are what the veterinary behaviour guidance recommends. A dog told off for urinating often learns to do it out of sight instead.
Safety note
Straining, blood in the urine, or drinking noticeably more means a veterinary appointment today rather than a training plan. The same goes for a dog who seems unwell in any other way. Do not wait to see whether it settles.
How long this takes
Nobody can promise you a number, and marking that started in adolescence often eases as the stage passes. What you control is access, cleaning and a boring outdoor routine that pays.
Today's version, in one line: enzymatic clean, doors shut, and an outdoor trip every 2 hours.