Wave

Wave gives away real double entry accounting and invoicing at no cost, and makes its money on payment processing and payroll. For a sole proprietor or a business under about ten transactions a week, it is the honest answer to "what should I use", and it has been for years.

What it does well

Invoicing is clean and the free tier is not crippled: unlimited invoices, unlimited estimates, unlimited customers. The ledger underneath is proper double entry, so an accountant can work with it rather than around it.

Tax and filing

Wave is a Canadian company and its payroll product reflects that: Canadian payroll files T4s and handles CPP, EI and ROEs directly, with automatic remittance to CRA in supported provinces. US payroll handles Form 941, W-2 and state filings in a limited set of states, and in the rest it calculates but leaves you to file. Check your state before you commit, because that difference is the single biggest gotcha here.

Sales tax is basic. You define rates and apply them. There is no nexus intelligence.

Where it frustrates people

Bank feed reliability is the recurring complaint and the reviews are consistent about it: connections drop and need reconnecting more often than on paid competitors. There is no inventory, no project tracking and no multi currency. Free support means email and a forum, and the response is not fast. Wave is excellent until you outgrow it, and you will know the day you do.