The amount of your check can go down if:

You’re receiving a pension based on any previous work, including a Social Security pension. They’ll calculate your weekly pension amount and reduce your weekly benefit by that amount. If the weekly pension amount is equal to or greater than your weekly benefit amount, you won’t receive any unemployment benefits.
You’re still receiving severance pay from your employer.
You owe child support. Your unemployment check may be cut by 25 percent and that money would be used for your child support payments.
You receive earnings from another job.
Paying taxes on your unemployment insurance benefits

Unemployment compensation benefits are taxable income. You can elect to have 10 percent of your payments automatically withheld for federal tax purposes, or you can make estimated quarterly tax payments. Quarterly payments are due January 15, April 15, July 15 and October 15.

Filing for unemployment should be the first item on your agenda when you’ve been laid-off. It might take two or three weeks to collect a check, so the sooner you file, the faster you’ll get paid. A delay in filing will mean a delay in collecting.