How long to acknowledge old passport?

Up to 20 days is the feedback I'm seeing on this forum

i think it depends which office your Docs were sent to, passport and Docs go into large bins which overflow, if Docs fall out onto the floor they get put into the bin behind which cause further delays plus the passport office are under pressure to process urgent queries which makes for the standard application to take longer.

Mine still says 'send your old passport' since it got signed for on the 4th of May. Not sure how long it will take. On the 15th I messaged HMPO on web chat and said they will add the Royal Mail tracking number onto the notes, but did not seem to make it quicker to update the progress of the application. Hopefully it will change next week.

Mine took 15 days at Peterborough

still waiting for mine to be received on day 25, phoned passport office and it appears no further action can be done until the office acknowledge receipt of the documents, very painful experience for a lot of people.

Finally got a message today, documents received 😃 applied 30th April. Signed for on 4th May at hmpo. Email/ text to say they’ve been received 26th May. One step closer .

Mine was delivered on May 5th. Still at the 'Send your documents' stage. And I need to fly in September. I thought that would have been plenty of time in advance...

44 days since my old passport was signed for at hmpo got a message yesterday saying if I don’t send old passport by 23 July they will cancel the application and I won’t get a refund. Absolute joke