Yes. One account, one set of API credentials, and as many projects, websites, and apps as you need. Nothing in our API limits you to a single application, and you choose which SenderID to use on every request.
For most developers this is the right setup. It keeps one balance to watch, one place to check your reports, and one integration to maintain.
Open a second account when you need to keep things genuinely apart:
Separate billing. Each account has its own credit balance. If you build for clients and each one pays for their own messages, give each client an account.
Separate SenderIDs. A SenderID belongs to a brand. If you send for several brands, each one needs its own SenderID, and it is cleaner to keep each brand in its own account.
Separate credentials. If a password leaks, only that account is exposed. Handing one set of credentials to three different development teams is a risk you don't need to take.
Separate reports. Each account has its own message archive, so a client sees their own traffic and nobody else's.
If none of those apply, stay on one account.
Sub-accounts don't create child accounts under a parent. They link accounts you already own so you can manage them from one login.
Once you link an account, you can switch into it from your own portal without typing its password again, and you can move credits between your accounts. Each linked account stays a full account: its own balance, its own SenderIDs, its own archive, and its own API credentials.
Linking needs the other account's consent. We send a code by SMS to that account's mobile number, and the link is active only after it's confirmed.
So the pattern most companies use is simple: one account per brand, department, or client, all linked together, and one person who can reach all of them from a single login.
Can I change, transfer, or hold multiple SenderIDs?
How do I activate API on my account?
How do I secure my API account?
+ What is a Blacklist/DND number, and how do I fix it?
+ How can I register my SenderID in other countries?