Here are some free indoor spaces in Toronto that are perfect for an engagement shoot, no permit required:

1. Toronto Reference Library
   This iconic library offers a beautiful interior with a spacious, open design. The dramatic spiral staircase and modern architecture make it a fantastic, free spot for photos. You can shoot in the main lobby area without any issue.

2. Allan Gardens Conservatory
   A hidden gem for an indoor shoot, this botanical garden offers lush greenery, tropical plants, and an airy atmosphere. The conservatory is free to visit and provides a natural, vibrant backdrop for engagement photos.

3. The Distillery District (Indoor Spaces)
   While the outdoor area is popular, many of the buildings in the Distillery District feature beautiful indoor courtyards and industrial interiors, perfect for a rustic and artsy shoot. Most of the indoor spaces in the public areas do not require a permit, though be mindful of the busier spots.

4. Art Gallery of Ontario (AGO) - Lobby
   While you will need a ticket to access the galleries, the main lobby area of the AGO is free to enter. The architecture is stunning with its wide open spaces, making it an ideal location for indoor photos, especially with natural light pouring in.

5. Eaton Centre - Interior
   The Toronto Eaton Centre is a bustling mall with a stunning architectural design. Its glass ceiling and modern interior make it an excellent spot for an urban, high-fashion look. You can shoot in the common areas without a permit, but be mindful of the crowds.

6. Harbourfront Centre (Indoor Spaces)
   While the outdoor space along the waterfront is lovely, the indoor spaces in Harbourfront Centre are also worth exploring. Many of the public areas are open and provide clean, minimalistic backdrops that work well for a relaxed engagement shoot.

7. The PATH (Underground City)
   Toronto’s PATH system has many underground walkways and modern spaces that have a unique, urban vibe. The wide hallways, sleek architecture, and glass-covered areas can give your engagement photos an edgy and distinctive feel.

8. St. Lawrence Market (Interior)
   Known for its historic charm, the interior of the St. Lawrence Market offers rustic brick walls and an authentic, old-world feel. The market is free to explore, and the interior provides a vibrant atmosphere, perfect for candid or playful engagement shots.

9. University of Toronto - Hart House (Main Lobby)
   Hart House has a beautiful interior with grand, open spaces, making it perfect for a more intimate indoor engagement shoot. You can often photograph in the main lobby or some of the public areas without a permit.

10. Queen Street West - Public Indoor Spaces
    Some stores along Queen Street West, particularly those with a vintage or artsy vibe, can be great spots for indoor engagement photos. Many shops and cafes allow photos without a permit, though it's always polite to ask before starting your shoot.

These locations offer unique and beautiful backdrops for free, making them ideal for couples on a budget while still getting fantastic, memorable engagement photos! Just remember to be considerate of other visitors and ensure that you’re not disrupting any regular activities.