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You best recourse is to request all of your documents back and take them to another firm. They are not allowed to withhold your documentation from you for any reason including non-payment. This time of year there are many accounting firms that have time to prepare past taxes. There is really no way to speed them up and once a relationship heads down this path there is really no way to be comfortable from either side. It is best to take your business elsewhere and start over. If you don't want to do this I would try to talk directly with the owners, if you already are then you are out of luck.