SEATTLE — Payment-processing company Square, readying an expected $275 million initial public offering, says it won’t renew a high-profile pact with Starbucks that brought it plenty of business – but big losses.

Eager for a powerful partner when it launched back in 2012, San Francisco-based Square took a $25 million investment from Starbucks and made the coffee company a marquee customer. But their love affair has unraveled.

Starbucks CEO Howard Schultz stepped down from the Square board in late 2013. And Square’s preliminary IPO filing this week sheds light on the financial side of the relationship.

The breakup will take away a significant chunk of its revenue: In the first six months of 2015, Starbucks transactions accounted for $63 million, or about 11 percent, of Square’s total revenue. But the deal also generated a $14 million loss for Square in those six months.

Accumulated losses since 2012 mean that Starbucks has cost Square a cool $84.5 million, or slightly less than a fifth of the cash it has burned through since then.

Square says in its filings that the deal with Starbucks, struck in the third quarter of 2012, was a “valuable catalyst” to build up a strong infrastructure, but its “historical terms are not representative of future economics.” Square says Starbucks was the only client representing more than 10 percent of its total revenues during the latest six months.

Starbucks didn’t immediately respond to a request for comment.

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