Do I have to be physically present to close, or can my lawyer sign for me?

No, you generally don't need to be physically present. Most business sale closings in Ontario happen as coordinated document and fund exchanges between lawyers, with the actual signing done in advance — in person at your lawyer's office, or in some cases electronically — and held pending final closing instructions rather than performed live at a closing table. You're rarely required to be sitting across from the other side when the deal actually completes.

Your lawyer signing "for" you is a different question, though. A lawyer generally can't just sign a contract or transfer document as your agent without specific authorization to do so — that requires a properly executed power of attorney or similar authorization covering exactly what needs to be signed. If you know in advance that you'll be unavailable on the anticipated closing date, raise it early so your lawyer can arrange either pre-signed documents or the right authorization, rather than discovering a gap in signing authority at the last minute.