Cover in private health insurance generally begins at the time stated as the start of cover in the policy document. The condition is that the contract has been concluded and no plan restrictions stand in the way.
Waiting periods can generally be agreed in private health insurance. By law, in comprehensive health insurance they may be no more than three months as a general waiting period and eight months as a special waiting period, for example for delivery, psychotherapy, dental treatment, dentures and orthodontics.
In practice, however, waiting periods often do not apply if you can prove uninterrupted previous insurance in Germany. If you switch directly from statutory health insurance or an existing comprehensive health insurance to private health insurance, your uninterrupted previous insurance period is usually credited.
It is still important: you must state planned, recommended or ongoing treatments correctly in the application. Crediting previous insurance periods does not automatically mean that every treatment already known is reimbursed without review.