How to prove financial hardship.

Along with what Nick has said, also keep ready your rent bills if you're staying in an apartment. Plus, keep your grocery bills along with transportation cost and health related expenses.
Also, you should have a valid reason of financial hardship like health problems, job loss, etc.
You should also be prepared with a timeframe within which the creditor can expect a positive change in your financial situation.

You have to provide meticulous details to convince your creditors. The specific requirements vary from creditors to creditors. But usually, you have to submit the following docs:

1. Pay stubs


2. Property tax bills


3. Income tax returns


4. Checking account statements for the last 6 months

Yes, you can show your financial hardship to the credit card company. But, showing the financial hardship is not enough to convince your credit card issuer. They will check your previous credit card bill payment records. If you were not regular on the bill payments, they will never listen to your financial hardship issue.

Usually credit card companies are hard to convince. But your pay stubs and Checking account statements might do the job. Ofcourse as Nick suggested, property tax bills and income tax returns may also explain your current situation to them. Tell me something. how many credit card accounts are you talking about?