Claims that the official Brexit campaign at the EU referendum may have exceeded spending limits is reported widely.
It is the Observer's lead, as it has an interview with Shahmir Sanni, who worked for the pro-Brexit group, BeLeave.
In its leader column, the paper says the allegations it has printed should trigger a debate about whether electoral laws are fit for purpose, because the "modern realities of electioneering" are putting "the principles of fairness and transparency under strain".
The Mail on Sunday is in agreement, arguing that the rules are "hopelessly out of date", having "only just caught up with the invention of television".
A dissenting voice comes from the Sunday Telegraph, which says that "trying to cancel the referendum, question its legitimacy or engineer a Brexit in name only would be a flagrant reversal of what the people had voted for".
The word hero is widely used to describe the French gendarme, Lieutenant-Colonel Arnaud Beltrame, who died from his injuries after swapping places with a hostage during Friday's supermarket siege.
Mr Beltrame's brother, Cedric, is quoted in the The Sunday Telegraph as saying "he gave his life for someone else, for a stranger. He departed as a hero".
The government is preparing to announce plans to put an extra £4bn a year into the NHS over the next decade, reports the Sunday Times.
It says there is a "growing realisation" in the cabinet that the health service is the Conservatives' "Achilles' heel" and follows months of lobbying by Boris Johnson and Jeremy Hunt.
Simon Walters, writing in the Mail on Sunday, says the Tories allowed Labour to claim the NHS was not safe in their hands, and Theresa May "has been forced to pay up to prove it is".
The Sunday Mirror's editorial says that there is no question the NHS needs more money, but queries where it will come from.
The paper says a special NHS tax should be considered, or a French-style insurance system, based on a sliding scale of income.
'What were you thinking?'
"Shamed", is the Sunday Times' headline as it reports on the Australian cricket team's admission that they tampered with the ball during the third day of the third Test against South Africa.
The Sydney Morning Herald's Peter Fitzsimons peppers his opinion piece with capital letters, as he asks the team's captain, Steve Smith, "WHAT WERE YOU THINKING?"
Calling for his resignation - or dismissal - he writes: "As a nation our name has been slurred, and as a nation, we must be seen to react. The first step is: Smith must go."
With Easter a week away, the Sun on Sunday is concerned that the word itself is being erased. It notes that in 2012, Cadbury's sold an Easter Egg Trail Pack, but that has since been renamed as the "Egg Hunt Pack".
The paper's editorial blames the "barmy politically-correct brigade", and wonders whether Christmas will be removed from Christmas puddings.
Elsewhere, the Sunday Telegraph says there is a "campaign" to turn Easter into a second Christmas, with the supermarkets adding Easter panettone, stollen and turkey to their ranges.
A new front has opened in the war on plastic, reports the Sunday Mirror, with teabags in the firing line. It says that Tetley and Yorkshire Tea are working to bring in a biodegradable bag. It adds that PG Tips has already promised to stop using plastic by the end of the year.
Pictures of Sir Paul McCartney, wearing a T-shirt with the slogan "we can end gun violence", are in several of the papers.
The Sunday Mirror notes that the former Beatle told a march in New York - one of 800 held in support of stricter gun controls following the Florida high school shooting - that John Lennon was shot dead not far from where they were gathered.
The Sunday Times, while querying whether the marches will result in change, says "the energy and fury" of the crowd means the pro-gun National Rifle Association "faces a movement that can easily match it for commitment, popularity and funding".
The readiness of Britain's armed forces is called into question by the Sun on Sunday, which reports that one in five military personnel is not "fit to fight".
Elsewhere, the Sunday Express reports that one in five of the Royal Navy's fleet of frigates and destroyers are available for operations.
The Sunday Telegraph says the return of cold weather over the Easter weekend looks set to add to travel woes and rail closures.
And if you do get where you need to go, the Sunday Mirror reports that the cost of parking a car is set to double in some seaside resorts over the holiday weekend.
The Sunday Times reveals that the music we listen to in our early teens stays with us for the rest of our lives. It quotes from a new book.