Working as an independent contractor for a US-based software development agency as a Canadian involves several considerations. Here are some steps and considerations you may want to take:

Understand Legal Requirements:

Check the legal requirements for working as an independent contractor in the US. Typically, you would need a work visa, such as an H-1B or an O-1 visa. However, as an independent contractor, you may also explore other visa options or consult with an immigration lawyer to determine the best fit for your situation.
Tax Implications:

Understand the tax implications of working as an independent contractor in the US. You may be subject to both US and Canadian taxes. Consider consulting with a tax professional who is knowledgeable about cross-border taxation to ensure compliance with both countries' tax laws.
Business Structure:

Decide on the business structure for your independent contracting work. You may choose to operate as a sole proprietorship, partnership, or corporation. Each structure has different legal and tax implications.
Contracts and Agreements:

Clearly outline the terms of your contract with the software development agency. Include details such as the scope of work, payment terms, project milestones, and any other relevant terms. Consider seeking legal advice to ensure the contract protects your interests.
Insurance:

Consider obtaining professional liability insurance and other relevant insurances to protect yourself in case of unforeseen circumstances.
Banking and Finances:

Set up a separate bank account for your business transactions. This will help you keep your personal and business finances separate, making it easier for tax purposes.
Remote Work Considerations:

Since you're working remotely, ensure you have the necessary tools and infrastructure in place. Consider issues like internet connectivity, communication tools, and a dedicated workspace.
Currency Exchange and Payment Methods:

Discuss with the software development agency how payments will be made, taking into consideration currency exchange rates and any potential fees associated with international transactions.
Visits to the US:

If your work requires you to visit the US, make sure you understand the visa requirements for short-term visits. If you have a work visa, ensure that it allows for such visits and the duration of stay.
Stay Informed:

Stay informed about any changes in immigration laws, tax regulations, or other relevant policies that may impact your work status.
It's crucial to consult with legal and financial professionals to ensure compliance with both US and Canadian laws and to address any specific details related to your situation. Each case is unique, and professional advice tailored to your circumstances is invaluable.