No. You can add as many debt accounts as you have, and that has been true of the free version since the site launched in 2012.
What is unlimited
- Debt accounts: credit cards, loans, medical bills, anything with a balance and a payment. Add as many as you need.
- Payment history: every payment and purchase you log is kept for the life of the account.
- Debt snowflakes: add as many extra or one time payments per month as you like.
- Payoff methods: every payoff order in the dropdown is available on every account.
If you read that the free version stops at 20 debts
A few comparison sites list a debt cap for the free tier. There is none, and there never has been. The pricing page lists unlimited accounts under the free column, and the only things Undebt.it+ adds are extra features such as bill tracking, YNAB sync, reminders and an ad free member area.
Does a long list slow anything down?
No. Members with 30 or 40 accounts use the site every day. If your list gets long, the account list page sorts and filters, and you can mark paid off accounts so they drop out of the active plan without deleting their history.