Whether you are in the USA and/or abroad, you are responsible for reporting the royalties you receive from the sale or streaming of your music. This isn't a Symphonic rule or policy but a government-enforced policy for all territories of the world.
Our system logs every payment and sale you make and thus we send you payments but from there, it is up to you to report.
From a USA / Domestic standpoint: We send out 1099's and other documentation on a yearly basis and at the appropriate time for you to report. We additionally report information in regards to your royalties to the IRS thus it's in your best interest that if we pay, you report. We suggest you immediately report whatever income we send you on a 1099-MISC to avoid tax issues.
For our international clients, the same above applies although there would be different forms associated with the reporting all of which are discussed here.