To find the sum of the series \(1 + 2 + 3 + \ldots + 98 + 999\), we need to recognize that this is not a simple arithmetic series because the last term jumps from 98 to 999. We can break it down into two parts:

1. The sum of the arithmetic series from 1 to 98.
2. Adding the number 999 to the result.

### Step 1: Sum of the series from 1 to 98

The sum of the first \(n\) natural numbers can be calculated using the formula:
\[ S = \frac{n(n + 1)}{2} \]

For \(n = 98\):
\[ S_{1-98} = \frac{98 \times 99}{2} = \frac{9702}{2} = 4851 \]

### Step 2: Adding 999

Now, we add 999 to the sum we obtained:
\[ S_{total} = 4851 + 999 = 5850 \]

Therefore, the sum of the series \(1 + 2 + 3 + \ldots + 98 + 999\) is \(5850\).