Take the example in the cropped image here. The writer here communicates a testing service which can indicate compliance or non-compliance with customer requirements. The writer also uses whether when the correct choice is to use if.
What is the difference? If is used only if the sentence has one possibility. Whether is used only if the sentence has more than one possibility (often connected with the coordinating conjunction or). While the fix here may be obvious, that obvious selection is only one option available to the writer.
Option #1: Exchange whether for if
The obvious choice remedies the sentence because the sentence contains only one object (requirements).
The writer can continue to use whether by providing an extra possibility. In this case, the possible results of the testing will be compliance or non-compliance, so the writer includes both possibilities in the sentence.
Use if when your sentence includes only one possibility. Use whether when your sentence includes more than one possibility. The mnemonic I use to know the difference lists both words in alphabetical order. Since if will come before whether, and 1 comes before 2, I know that if is used with one possibility while whether is used with more than one possibility.
Whether you choose to remember with this device or another of your own choice, your writing will be clearer and cleaner when you use if and whether correctly.