Is it permissible to make up missed Ramadan fasts during days of doubt and two days before Ramadan, knowing that the Prophet (peace and blessings of Allah be upon him) forbade fasting on days of doubt and two days before Ramadan?

It is permissible to make up missed Ramadan fasts one or two days before the next Ramadan, because it is an obligation and it is not permissible to delay it until after the following Ramadan. Fasting on the Day of Doubt and anticipating Ramadan by fasting one or two days has been prohibited, except for someone who has a habit of fasting. In this case, if voluntary fasting that is habitual is permissible, then making up Ramadan fasts is even more deserving of permissibility because it is an obligation. Al-Nawawi mentioned that fasting on the Day of Doubt to make up a fast, fulfill a vow, or perform an expiation is sufficient.