The US Postal Service is hoping to win a bigger slice of the $90bn US media advertising market by offering some of the nation’s top advertisers a money-back guarantee to test out direct mail campaigns.

From as early as next month, it will be offering 16 major advertisers the chance to try out direct mail in a market trial called “Mail Works Guarantee”.

The companies will be those spending at least $250m a year on advertising, but do not currently use the mail for a significant amount of promotional activity – those where postage represents less than 0.36% of their advertising budgets.

The companies taking part in the Mail Works Guarantee trial, which could last up to two years, will each be expected to mail between 500,000 and a million mailpieces of First Class Mail or Standard Mail.

Should the direct mail campaign to achieve a number of agreed targets, the USPS would provide a refund of postage costs, up to a maximum of $250,000.

Targets might include an increase in store traffic for large retailers, an increase in web traffic for e-commerce companies or an increase in sales for a product or goods supplier.

Refunds would not cover print and production costs, and would be paid out as credit, according to documents filed with US regulators on Friday.