There is again no one size fits all answer to this question.
There are a number of risk factors. If the dog is young, entire, hunts or is fed a raw meat diet the risk is seen as high for round worms. To be safe a dog should then be wormed monthly. If the dog is purely indoor, fed dog food and does not hunt then the risk is minimal for round worms.
Tapeworms have a number of risk factors. The more serious tapeworms are found in the Hebrides and Powys and the surrounding area. Animals living or visiting those areas regularly MUST be wormed 4-6 weekly for tapeworm. The other high risk factors are hunting, having fleas or lice and being fed raw meat and in these cases again monthly treatment is necessary.
Most dogs with effective flea control, fed normal foods and not hunting are best wormed quarterly.