Cash transactions at Post Office branches totalled a record £3.48 billion in April.
Across the UK, £2.62 billion was deposited by people and businesses in April.
Some £864.9 million-worth of withdrawals also took place.
Many banks have an agreement with the Post Office, enabling the banks’ customers to carry out routine transactions in post offices.
The Post Office recently partnered with Monzo to expand its everyday banking services and it said this contributed positively to the total value of cash deposit and withdrawals in April.
Ross Borkett, banking director at the Post Office said: “Post Office is delighted to welcome Monzo as another partner in our banking framework, helping us ensure more UK banking customers than ever before can access essential cash services in any Post Office branch.
“It is positive to see the continued growth in customers using their local Post Office, and accessing essential cash services through our extensive partnership with banks. The fact that we are seeing the highest ever levels of cash withdrawals and deposits demonstrates the growing importance of our services in providing access to cash for customers and businesses across the UK.”
Last week, Cash Access UK, an organisation set up to help protect access to cash, said a milestone of 50 banking hubs being opened had been reached.
The hubs, where banks share facilities, help to plug gaps for communities as bank branches close.
They have a counter service operated by the Post Office, allowing customers to conduct routine banking transactions.
Hubs have a private area where customers can consult with staff representing their respective banks for more complex matters.
Banks participating in each hub operate on a rotational basis, so staff from different banks are present on varying days.