How can I make invoices auto attach my terms of agreement .I keep forgetting to add it as an attachment to the invoice

You can only link your terms of agreement manually in the Attachments field of your invoices, accounts611.

We recognize the relevance of automatically attaching files to your invoices. However, this option is currently unavailable. You'll need to manually add them while creating your transactions.

That being said, I encourage you to submit this valuable idea to our product engineers for consideration in future updates. To send your feedback, follow these steps: 

1. Log in to your QuickBooks Online account.
2. Go to the Gear icon in the upper right and choose Feedback under Profile.
3. Type in your recommendation in the Share your feedback field.
4. Click Next to submit.  

If you have further questions, let us know in the comments.