If you allow too much tax to be withheld, you get a refund. You can determine how much is tax is taken out of your pay by the number of allowances you claim on your W-4. The W-4 has a worksheet to help you figure out how many personal allowances to take.
Step 5: Predict your next period. Now that we know how long your period cycle is, we can just use it to count the days to predict your next period. My period cycle is 28 days so if I count 28 days from February 10, that's when my next period should come.
So here is something simple to help you. This calculator lets you put in the date of your last period and instantly see when you are next due based on a 28-day cycle. Of course not every woman has an exact 28-day cycle. If yours is 30 days then simply add two more to the date shown. If your cycle is 26 days you will get it two days earlier than shown and so it goes. If you have an irregular cycle then unfortunately there is no way of predicting when your next period will be.