On the 20th of March, Monsieur de Serizy did not go to Ghent.
He informed Napoleon that he remained faithful to the house of Bourbon; would not accept his peerage during the Hundred Days, and passed that period on his estate at Serizy.
After the second fall of the Emperor, he became once more a privy-councillor, was appointed vice-president of the Council of State, and liquidator, on behalf of France, of claims and indemnities demanded by foreign powers.

Without personal assumption, without ambition even, he possessed great influence in public affairs.

Nothing of importance was done without consulting him; but he never went to court, and was seldom seen in his own salons.

This noble life, devoting itself from its very beginning to work, had ended by becoming a life of incessant toil.
The count rose at all seasons by four o'clock in the morning, and worked till mid-day, attended to his functions as peer of France and vice-president of the Council of State in the afternoons, and went to bed at nine o'clock.

In recognition of such labor, the King had made him a knight of his various Orders.