In more than twenty years of grooming I have heard the same sentence more times than I could count. I brush him all the time. And the owner is almost always telling me the truth. The brushing is real. It is just not reaching where the problem is.
A mat is not a knot on the surface
Coats do not mat from the outside in. They mat from the skin out. Hair that has shed does not always fall clear of the coat, particularly in the doodle crosses that are so common on the Gold Coast, where the coat holds on to everything it loses. That trapped hair sits against the skin, wraps around the hair still growing, and forms a small dense pad you cannot see and often cannot feel through the top coat.
A slicker brush skimmed over the top will glide beautifully across a coat that is matted underneath. The dog looks brushed. The top layer is brushed. Nothing below it has been touched.
This is the first thing I teach students at the academy, because it is the single most common mistake made by people who genuinely care about their dog.

The comb test
Here is the check that settles it. When you have finished brushing, take a metal comb and try to run it from the skin outward, right down at the base of the coat. If it passes through cleanly, you have done the job properly. If it stops, snags, or will not get in at all, there is matting there no matter how much brushing has gone on.
Do this in the places that mat first, because they are always the same places. Behind and under the ears. In the armpits. On the chest where the harness sits. Along the collar line. On the back legs where they rub together. Around the base of the tail. Friction and moisture are what start a mat, so anywhere two surfaces move against each other is where you look.
Wet coats are the fastest way to a matted dog
A swim, a bath at home, or a walk in the rain, followed by a coat left to dry on its own, will tighten existing tangles into mats faster than anything else I know. Water swells the hair, the coat dries down onto itself, and what was loose in the morning is solid by the evening. If your dog gets wet, they need drying and brushing out properly. A towel and a sunny spot is not drying.
This is a large part of what a professional blow dry actually does, and it is the part owners tend not to realise they are paying for. It is not about looking fluffy. Forced air separates the coat right down to the skin, and no amount of towelling achieves that.
What we will and will not do
When a coat is matted there are two options. Work it out, or clip it off. Which one applies depends entirely on how tight it is against the skin, and that is a judgement I make with my hands on the dog rather than from across the room.
We are bound by a code of ethics under animal welfare legislation, and we will not de-matt a coat where doing so would cause real pain. Dragging a comb through a tight pelt hurts. It bruises and tears the skin underneath, and it teaches a dog that grooming is something to dread. Once a dog has learned that, it can take years to undo, and I have spent a good part of my career undoing it in animals that other people rushed.
If we reach that point we will explain why, clip the coat off, and show you how to stop it happening again. That conversation disappoints people sometimes, particularly when a long coat has taken years to grow. I would still rather have it than hurt your dog for the sake of a haircut.
Keeping on top of it
Brush to the skin rather than over the top, and use a comb to check your own work. Do the friction points every time, not just the easy back and sides. Dry the coat properly whenever it gets wet. Take the harness off between walks if the coat underneath is soft. And book grooms on a rhythm rather than waiting until the coat looks bad, because by the time it looks bad from the outside it has usually been matting underneath for weeks.
If you are not sure whether what you are feeling is a mat, bring the dog in and one of us will show you. It is far easier to understand with a hand on the coat than from a page.