WhatsApp: The deal was first agreed in February, but only received EU approval last week.
Facebook's share price opened broadly flat today after its long-awaited deal to take over WhatsApp completed.
But the deal has ended up costing Facebook nearly $3bn more than was originally intended, because of the amount of time taken to get approval.
The deal – in which WhatsApp shareholders received 177.7m Facebook Class A shares and around $4.59bn (£2.86bn) in cash, while employees received 45.9m restricted stock units – was first agreed back in February
but only got EU approval last week.
Originally that meant the deal was valued at around $19bn, but because Facebook's shares have risen 13 per cent since the original offer, the total bill now stands at $21.8bn.
The deal also sees Jan Koum, co-founder and chief executive of the texting app, become a member of Facebook's board.
He will not be eligible for a bonus, though he does receive “an inducement grant” of more than 24.85m restructured stock units. These units will vest in quarterly periods over the next four years, with the first on November 15, 2015.
Koum will not receive any additional compensation as a member of the board and will not serve on any committees.
Facebook's share price hovered around the opening level of $77.4 per share on early trading.
UPDATE: This story has been updated to show the new value of the deal.