As reported by Doctor of Credit, Plastiq is sending out a targeted offer for 2 months of rent or mortgage payments with no service fee when you schedule 6 months of payments and pay with a Mastercard.
Plastiq normally charges 2.5% for Mastercard payments, though they target some people/accounts for a 2% fee on Mastercard payments. As this promotion offers two months free out of six total months of payments, your net fee savings will be 33% — dropping your net fee for six months of Mastercard payments to either 1.66% or 1.33%. Using a 2% back card will net you a small profit. Alternatively, some Plastiq payments code for 3X with a Citi AT&T Access More card, though this does not always seem predictable.
To qualify for the promotion, the first payment must be scheduled by March 31st.
To read more about this deal, see this Doctor of Credit post.