The answer to that question depends on the situation and what you're trying to do. There are streamline products available through your current lender that will allow you to, basically, refinance your mortgage by signing a bunch of papers.
There are also new programs out through Fannie Mae, Freddie Mac that will allow for a higher LTV than usual (up to 105%). If your current balance isn't too close to the appraised value from last year, they might not even require a new appraisal.
Most times, however, an appraisal is done everytime you refinance. But, there are programs out right now that are relaxing on these requirements.
If you need any help with a refinance, let me know. I can walk you through the process and place your loan.
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