The Conservative Party has been fined £70,000 after the Electoral Commission found more than £250,000 in election campaign expenses was missing or inaccurately recorded.
It's the largest fine ever issued by the Electoral Commission, outweighing the previous biggest penalty of £20,000 - slapped on the Labour and Liberal Democrat parties last year - by a considerable margin.
Here's what you need to know:
What were the allegations?
The Electoral Commission launched its investigation in February 2016 after concerns were raised by Channel 4 News that the Tories' campaign spending return for the 2015 general election may have been incomplete.
They also claimed that the party's spending in the 2014 European Parliamentary election was also suspect.
Investigators looked at whether the Conservatives had submitted complete and accurate spending statements; whether anything had been omitted; whether any invoices or receipts were missing; whether campaign costs relating to the transport of activists on the 'Battlebus' had been correctly reported; and whether there was any evidence that the party's treasurer had "knowingly or recklessly" made a false declaration of accuracy.
This involved the two above elections, as well as three by-elections in 2014 in Clacton, Newark and Rochester and Strood.
What did they find?
- £104,765 of payments in total were missing from the 2015 general election spending return
- Up to £118,124 was either not reported or was inaccurately reported
- At least some of the reported £38,996 Battlebus expenditure should have counted towards candidates' budgets, rather than counted as party spending
- £63,486.83 of Battlebus expenditure was not included in the report due to "human error"
- 81 payments to the value of £52,924 were missing the required invoices or receipts
In its report, the Commission concluded there was no evidence that the party's spending return for the European Parliamentary election was incomplete.
However, it said it was "likely" that expenses filed by candidates at the three by-elections in 2014 "understated the value" of spending on their campaigns.
Party treasurer Simon Day failed to properly account for and explain the party's dealings with the candidates and/or their agents for these by-elections, the Commission added.
In addition, the 2015 general election expense report was, in fact, incomplete and failed to include all the required invoices and receipts it should.
Mr Day had included payments which should not have been incurred by the party, including the use of the 'Battlebus' in marginal seats.
The Commission said, while the Tories had argues the bus was campaigning for a national victory - not for individual candidates - social media posts revealed activists holding posters and banners for candidates in the constituencies visited. This meant some of the Battlebus spending should have counted towards the budgets of those candidates, not the main party.
Mr Day also omitted payments which should have counted towards the party's budget, including accommodation for activists campaigning on location.
What are the punishments?
The Conservative Party has been fined a total of £70,000 for the contraventions of electoral spending laws.
It has until April 13 to pay the total.
The Commission has also sent a report to the Metropolitan Police, claiming that Mr Day may have committed a criminal offence by signing a formal declaration that the spending report was complete and accurate when it was not.
What else did the Electoral Commission say?
The Commission has criticised inaccurate spending reports as "undermining voters’ confidence" in the democratic process, as it could give some candidates an unfair advantage over others.
It also accused the Tories of "unreasonable uncooperative conduct", which it said had delayed the release of information vital to the investigation.
Chairman of the Commission, Sir John Holmes, has now called for more powers to punish political parties who break the rules, to stop them seeing fines as just a "cost of doing business".
His comments came as the Conservatives became the third major political party to face a fine over campaign spending.
Labour and the Liberal Democrats were both fined £20,000 last year for undeclared spending in the 2015 general election.
What has the party said about it?
A Conservative Party spokesman said it would pay the fines imposed without argument.
However, he called for a review of the Electoral Commission's requirements, saying they could be "clarified" to avoid similar errors in future.
He also disputed that any Battlebus spending should have been attributed to candidates in specific constituencies, saying there was "no reason not to declare it" in the national return.
“MPs in constituencies visited by the battlebus would have no reason to consider whether it should be included in their local return – they were directed that the bus would be visiting as part of CCHQ’s national spending," he added.
“The ongoing investigations relate to national spending by CCHQ and the national Party will continue to co-operate with the police and other authorities so that the matter can be resolved as soon as possible.”