The Queen will represent the King at the annual Royal Maundy service and distribute unique coins to community stalwarts from across the country.
Camilla will deputise for Charles, who is continuing to receive treatment for cancer, when the ancient ceremony is held at Worcester Cathedral on March 28.
Since his diagnosis, the King has postponed all public-facing duties but is continuing with behind-the-scenes work on his red boxes of state papers.
The Royal Maundy Service is a major fixture on the royal calendar and normally the monarch presents the specially minted coins to people recognised for their community service.
It is likely the King will also miss the annual Commonwealth Day service next Monday at Westminster Abbey when an address from the monarch to the family of nations normally features.
The Bishop of Worcester, Dr John Inge, who as Lord High Almoner will accompany the Queen as she presents the Maundy money, said: “It is an honour to be able to welcome Her Majesty the Queen to Worcester.
“This is an immensely special service and I know it will mean a huge amount to those who have been chosen to receive the coins, all of whom will have given years of service to their local communities.”
The Royal Maundy service is an ancient ceremony which originated in the commandment Christ gave after washing the feet of his disciples the day before Good Friday.
Today sovereigns no longer wash the feet of the needy, but each recipient is presented with two purses, one red and one white, filled with Maundy money.
Camilla accompanied the King when he presented the coins last year at York Minster and could be joined by other members of the royal family at the ceremony in Worcester.