A bidding war with Salesforce forced Microsoft to pay nearly $6bn more for its proposed acquisition of LinkedIn.

Details of the bidding were revealed in a filing with the Securities and Exchange Commission (SEC) ahead of a shareholder vote to approve the agreement.

Microsoft originally offered $160 per share, which would have valued LinkedIn at $21.22bn.

The filing mentions a Party A as also making a bid. Salesforce CEO Marc Benioff recently confirmed his company was also involved in bidding.

LinkedIn also approached three other unnamed companies on making a bid, but they all declined.

Google and Facebook were also reported to have shown interest in acquiring LinkedIn.

Microsoft finally agreed to buy LinkedIn last month for $26.2bn, or $196 per share in cash. It was a 50% premium over LinkedIn’s stock price prior to the agreement’s announcement.

The high price that Microsoft ended up paying is expected to result in deeper cost-cutting at LinkedIn upon the completion of the deal.

Microsoft CEO Satya Nadella indicated Jeff Weiner, his counterpart at LinkedIn, that a discussion of cost synergies in the transaction would be required in connection with any potential price increase from Microsoft.

On 9 June, Nadella met with Weiner to discuss integration planning and potential cost synergies arising from the combination and the status of the transaction generally.

On 10 June, LinkedIn’s chief financial officer Steven Sordello sent Amy Hood, Microsoft’s chief financial officer, an analysis of potential cost synergies arising from the combination.

Later that day, Sordello and Hood discussed various potential cost synergies arising from the combination, after which the agreement was signed.