You try your best. You model your cash flow. But you still come short. How do you fix it?
You can try calling your suppliers and negotiate better deals in vendor financing. It's not an easy conversation to have, but often wort to have.
You can try calling your customers. Try collecting your payments sooner, try getting some advances toward your payments.
If that isn't enough, it's time for short-term financing.
Call your bank and have a long hard discussion about your needs, they might give you some options:
1) Line of credit 2) Short-term loan 3) Invoice financing 4) Trade financing
A line of credit is a simple overdraft for businesses. It is a source of funds available to you at any time, agreed upon before you really need it. That means that unless you break through some covenants regulating your company, the bank will not take this option away when you need it.
Short-term loan is exactly what it says on the tin. You go to bank, explain why you need to borrow money for 3-6 months and if they give it to you, you can borrow it. The terms aren't too terrible and you either return it all in one or in periodic repayments.
There are some banks that offer invoice financing. Simply put, you show them your accounts receivable and they advance you about 80 % of the nominal amount. When you get paid back, you pay back the loan with interest.
If your business is in import/export, you can use trade financing. Trade financing provides guarantees to supplier and credit to buyer to facilitate transaction a diminish risk. Banks provide payment to supplier in time and extend the credit to the business until they can get paid.
Too many options? There are even more. And they are not offered only by banks, but by private and institutional investors as well.
The most important part is not to panic. When your model indicates temporary cash problems, find yourself a good line of credit or other credit facility and grow into it.