A Parliamentary crest on advertising shows it was funded by the taxpayer.
A spokeswoman for Parliamentary Services said it would also check election expense returns for anything it had paid for and invoice parties and MPs accordingly.
In previous years, parties could still issue taxpayer-funded material setting out their policies and priorities as long as there was no overt plug for votes, donations or new members. While that rule is the same during most of the Parliamentary term, the much tighter definition applies during the campaign period.
The Electoral Commission has already referred four advertisements to the police for alleged breaches of the Electoral Act, mostly the requirement for promoter statements.
Chief Electoral Officer Rob Peden said the commission had so far received 470 requests for advisory opinions on advertising intended for the campaign, some of the requests containing multiple advertisements.
Clear guidance had also been sent to candidates and MPs on the new rules with extensive examples.
Labour's campaign spokesman Grant Robertson said they had sent multiple advertisements in for testing - wary of being caught out by different views of the law.
All candidate material also had to be vetted by a committee and all MPs had been advised not to use Parliamentary Services material.
* The start of the regulated period also marks the start of the spending limit - parties with candidates in every seat can spend up to $2.8 million on their campaign. Spending limits of $300,000 apply to interest groups or people who campaign during the election period. So far eight groups - seven of them unions - have registered as "promoters". Ten groups had registered as promoters for the referendum on MMP.
ELECTION PERIOD
* The regulated election period begins today.
* Under new electoral laws, Parliamentary funding can now only be used for the most basic material.
* Parties have to pay themselves for anything setting out their policies and candidates.
* If Parliamentary-funded material is used, the MP or party will have to repay a portion of its cost to Parliamentary Services.