Banked points must be used prior to the end of the next use year. So if your use year is April, and you want to bank points from the 2001 use year, you must use them for a stay between April 1, 2002 and March 31, 2003. If you don't you lose them. Banked points also cannot be returned to their original use year.
With an April use year, you can bank up to 100% of your 2001 points as long as you talk to MS on or before September 30, 2001. You can bank up to 50% of your points up to the end of December, 2001. Up to 25% can be banked up to the end of January, 2002.
Banking percentages are based on the CUMULATIVE number of points that are banked as of the banking deadline. For example, let's say you have 200 points and in September, you decide to bank 125 of then. You would then NOT be able to bank any more points after the end of September because the number of points already banked would be greater than 50%.
Hope that helps. If not, just ask.
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