Mr Paisley had already apologised for what he said was his "unintentional failure" to register the hospitality, which he estimated was worth £50,000.
The commissioner, which said the cost may have been "significantly more" than Mr Paisley's estimate, said the Sri Lankan holidays in 2013 included business-class air travel, accommodation at first-class hotels, helicopter trips and visits to tourist attractions for the North Antrim MP and his wider family.
The watchdog's finding read: "In view of the seriousness of this matter, we recommend that Mr Paisley be suspended from the service of the House for a period of 30 sitting days starting on 4 September 2018."
The commissioner also said Mr Paisley should now register the holidays with the parliamentary authorities.
Generic stock photo: A beach in Sri Lanka
The recommendations will need to be approved by the House of Commons before being confirmed. Mr Paisley is due to address the House on Thursday.
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