To check your transactions click Transactions in the HQ+ menu.
Here is a guide to what the different types of transactions you will see:
'Received' - This indicates an amount of postcard credits you have received and who from.
'hq-postcard' - This indicates an ad-hoc postcard being sent from the 'Event Postcards' tool. It shows the recipient and the cost.
'FP BD card' - This indicates an automated birthday card being sent, the recipient and the cost.
'FP Review' - This indicates an automated review card being sent, the recipient and the cost.
'Transferred' - This indicates and amount of Postcard credits you have sent and the recipient.