Put simply, no.
When the Energy Performance Certificate is issued it will include some recommendations to help you save energy, reduce your energy costs and reduce your CO2 emissions. The certificate will also give you an idea of the typical cost of making these improvements and the savings you might see on your energy bills.
However, these improvements are not mandatory and it is up to you to decide whether or not you want to make them. You will want to consider how quickly the savings will pay for the improvements and what impact the changes will have on your property. In some cases you may not even be permitted to carry out the necessary works for example, you may live in a conversation area and the changes may not be permitted.
In the future some buildings with very low ratings may have to have improvements carried out to improve their overall rating. Even so, it will be up to the owners to decide which improvements they wish to make. From April 2018, landlords will not be permitted to rent out most properties in England and Wales with an F or G EPC rating to a new tenant.