The Labour Leader failed to register eight separate interests on time which included declaring gifts from football teams and the sale of a plot of land.
Sir Keir has apologised to the Parliamentary Standards Commissioner Kathryn Stone for what the party said was an “inadvertent error”.
The inquiry was opened into the Opposition leader by Ms Stone in June following claims regarding late declarations of gifts and other benefits from UK sources.
Sir Keir Starmer broke MPs’ code of conduct eight times, inquiry finds
At the time, Starmer insisted that he was “absolutely confident” that he had not breached the code.
Since then, Ms Stone has discovered that Sir Keir failed to declare eight interests – which is reportedly five more than was noted in the original complaint.
Sir Keir received an £18,450 advance from publisher HarperCollins in April for a book he is writing where he is expected to set out his vision for Britain.
The advance, which he has pledged to donate to charity, was declared a day late while royalties for two legal books published before the lawyer became an MP were also delayed.
Starmer also received a directors’ box for two people at Crystal Palace worth £720, when they thrashed his club Arsenal 3-0 on April 4. It was not registered until May 5.
Worth a total of £1,416, Sir Keir received four tickets for Watford vs Arsenal, for their March 6 match which was later registered on May 6.
Just Eat also gave tickets to staff for the Taste of London festival and the British Kebab awards.
This gift exceeded the £300 limit for registration on October 29 but was not declared until December 23.
In the original complaint made to the commissioner, it was alleged that between March 6, 2022 and May 13 2022, Sir Keir had failed, on three occasions to register income and hospitality that he had accepted, within the 28-day deadline set by the House.
The watchdog undertook a review of Sir Keir’s register entry over the last 12 months and noted four additional late entries.
The Commissioner has noted that the “breaches were minor and/or inadvertent and that there was no deliberate attempt to mislead”.
The inquiry has therefore been concluded by way of the “rectification” procedure.
This involves publishing the details and an apology on the Commons website but does not require a referral to the Committee on Standards.
A referral to the Committee occurs in more serious cases.
A Labour Party spokesperson has said that following the verdict that Sir Keir takes his responsibilities to the register of interests “very seriously and has apologised to the Commissioner for this inadvertent error”.
“He has assured the Commissioner that his office processes have been reviewed to ensure this doesn’t happen again,” they added.