Subordinating Conjunctions With Coordinating Conjunctions

Subordinating conjunctions spark some confusion for some non-native writers of English. When using a subordinating conjunction at the beginning of a sentence, you do not need to use its coordinating equivalent after the comma. Take these examples:

Example 1: Although it was raining yesterday, but Billie still ran three laps around the neighborhood. → Although it was raining yesterday, Billie still ran three laps around the neighborhood.
Example 2: Since the last tax season already ended in April, so you should file for late tax returns. → Since the last tax season already ended in April, you should file for late tax returns.
Example 3: After we submitted the marketing proposal for a new campaign, and then we went out to dinner at our favorite pizza place. → After we submitted the marketing proposal for a new campaign, we went out to dinner at our favorite pizza place.

You would use a coordinating conjunction to link two independent clauses, but the subordinating clause cannot stand alone as its own sentence. Therefore, the correct move here would be to simply add a comma after the subordinating clause without a coordinating conjunction. You can also take out the subordinating conjunction instead of the coordinating conjunction as so:

Example 1: It was raining yesterday, but Billie still ran three laps around the neighborhood.
Example 2: The last tax season already ended in April, so you should file for late tax returns.
Example 3: We submitted the marketing proposal for a new campaign, and then we went out to dinner at our favorite pizza place.

Here are some common subordinating conjunctions so you can make sure to double-check the next time you use one.