Unemployment insurance helps you get by after you've lost your job. You may wait to file for unemployment for a variety of reasons, such as receiving severance pay or not realizing that you might be eligible. If there was a gap between the time you lost your job and the time you opened your unemployment claim, you may be able to get payment for those weeks that you didn't claim.
In a typical scenario, the "waiting week" starts the Sunday before the day that you file for unemployment. You are not allowed to receive payments for the waiting week.
States treat unemployment compensation differently. Though some states may not pay you for the weeks you waited to file, others might. The process to claim back weeks may also vary. For example, Washington state allows you to claim back weeks if you call through the telephone system rather than using the online system. If you are not sure whether you qualify, contact the Department of Labor.
Some states do not allow you to apply for unemployment compensation if you received a severance package. For example, if you received two months' salary as severance, you'll have to wait two months to apply.
The Good News
States allow you to receive a certain number of weeks of unemployment compensation. If you wait three weeks to apply for unemployment, you do not lose those three weeks of payment; rather, you'll extend the length of time that you are eligible for unemployment.