Can we write off e-transfers without a receipt? I am self-employed and renovating basement to rent it out.

I am assuming you are asking if you can write off an expense that was paid by an electronic means, but you do not have a receipt for it.  The answer is that if it is a legitimate expense for your business, then it can be included on your tax return.  However, you do need to have some sort of substantiation for that expense.  If your return is audited for any reason and there is no substantiation to prove the expense, it will be disallowed.  Do what you can now to back up that expense with some documentation while it is still fairly current.

Please give more details for your question if this is not what you were trying to ask.