If your cat suddenly lies on its back with its belly exposed, legs in the air it is a sign that your cat trusts you as the belly is a very vulnerable area. If the facial expression is relaxed and the tail is still your cat may be inviting you to give him a belly rub. Start by stroking the head first and gently move down to the chest, giving it a gentle slow massage. If you feel no tension in the body then move down from the chest to the tummy in slow relaxing strokes while talking in a calm voice.
Be wary as a cat can quickly grab your hand with the front paws and kick your forearm with the back paws while biting you simultaneously leaving you in need of some first aid if you have not interpreted their body language correctly. Over time you will get to know when you can and can’t give a belly rub once you and your cat know each other well and you understand your cat’s body language.
Cats also lie on their backs when in a playful mood. So if their eyes are watching your every move and flicking their tail at the same time quickly, they are inviting you to play, not to rub their belly. A teaser toy or a kick toy would be the ideal choice to offer your cat. If you were to mistake these signs for an invitation to give a belly rub you risk a teeth and claw attack on your hand and forearm.
Do remember the tail is a great indicator and if it is rapidly flicking a tummy rub will be the wrong decision!
Cats often lie on their backs when sleeping. Usually they curl up to sleep but stretch out in order to cool down. It is never a good idea to wake a cat sleeping on its back with a belly rub, no matter how cute they look, if you want to avoid being bitten or scratched!