How to retrieve data from a C file efficiently

I have a program that is supposed to retrieve (on start-up) data from a text file. This file may get huge and I was wondering how I could speed up the process and assess its current performance. The code used to retrieve data is as follow:

void startUpBillsLoading(Bill *Bills)
{
    FILE *BillsDb = 0, *WorkersDb = 0, *PaymentDb = 0;
    BillsDb = fopen("data/bills.db", "r");
    WorkersDb = fopen("data/workers.db", "r");
    PaymentDb = fopen ("data/payments.db", "r");
    char *Buffer = malloc (512);

    if (BillsDb && WorkersDb && PaymentsDb)
    {
        int i = 0, j = 0;

        while (fscanf (BillsDb, "%d;%[^;];%[^;];%[^;];%[^;];%d/%d/%d;%d/%d/%d;%d;%f;%f\n",
                &Bills[i].Id,
                Bills[i].CompanyName,
                Bills[i].ClientName,
                Bills[i].DepartureAddress,
                Bills[i].ShippingAddress,
                &Bills[i].Creation.Day,
                &Bills[i].Creation.Month,
                &Bills[i].Creation.Year,
                &Bills[i].Payment.Day,
                &Bills[i].Payment.Month,
                &Bills[i].Payment.Year,
                &Bills[i].NumWorkers,
                &Bills[i].TotalHT,
                &Bills[i].Charges) == 14)
        {
            Bills[i].Workers = 
                malloc (sizeof(Employee)*Bills[i].NumWorkers);

            fscanf (PaymentDb, "%d;%d;%[^;];%[^;];%[^\n]\n",
                    &Bills[i].Id,
                    &Bills[i].PaymentDetails.Method,
                    Bills[i].PaymentDetails.CheckNumber,
                    Bills[i].PaymentDetails.VirementNumber,
                    Bills[i].PaymentDetails.BankName);

            LatestBillId++;
            i++;
        }

        i = 0;
        while (fscanf (WorkersDb, "%d;%[^;];%[^;];%f\n",
                    &Bills[i].Id,   
                    Bills[i].Workers[j].Surname,
                    Bills[i].Workers[j].Name,
                    &Bills[i].Workers[j].Salary) == 4)
        {
            for (int j = 1; j <= Bills[i].NumWorkers-1; j++)
            {
                fscanf (WorkersDb, "%d;%[^;];%[^;];%f\n",
                                &Bills[i].Id,   
                                Bills[i].Workers[j].Surname,
                                Bills[i].Workers[j].Name,
                                &Bills[i].Workers[j].Salary);
            }
            i++;
        }

        fclose(BillsDb);
        fclose(WorkersDb);
        fclose(PaymentDb);
    }
    else
        printf ("\t\t\tImpossible d'acceder aux factures !\n");

    free (Buffer);
}

I have used the time.h library to measure the time it takes to retrieve all the required data. A Bill's data is separated in 3 files: bills.db, workers.db and payments.db. Each file line from the bills.db and from payments.db represents an entire bill whereas in workers.db the amount of lines required to represent a bill is variable and depends on the numbers of employees that are related to the bill.

I created these 3 files in this way:

• bills.db and payments.db has 118087 lines (thus as many bills)
• Each bill was set (arbitrarily) to have 4 workers therefore, the workers.db file has 118087*4 = 472348 lines.

The time taken by this function to run completely is around 0.9 seconds. How good (or bad) is this time and how to improve it ?