To do this you will need to have taken a loan out from the bank. Everyday you will need to pay part of that loan back to the bank to continue to be able to take out loans. You will need to pull out multiple loans to be able to get this achievement. The longest you can take to repay a loan is 14 days. The longer you take to pay back the loan, The more you will have to pay back in total, but the less you have to pay back per day. You can check your progress on the Manager Blackboard under the Statistics section. Once "Invoices Paid" reaches 50 you are good.
This achievement will unlock after you close your store for the night after you have paid your 50th invoice.